drop the base (hahaha), no but seriously drop the -base from our vars since it's cleaner

scss/_breadcrumb.scss

@@ -8,7 +8,7 @@
   margin-bottom: $spacer-y;
   list-style: none;
   background-color: $breadcrumb-bg;
-  @include border-radius($border-radius-base);
+  @include border-radius($border-radius);
 
   > li {
     display: inline-block;

scss/_button-group.scss

@@ -183,11 +183,11 @@
     border-radius: 0;
   }
   &:first-child:not(:last-child) {
-    border-top-right-radius: $btn-border-radius-base;
+    border-top-right-radius: $btn-border-radius;
     @include border-bottom-radius(0);
   }
   &:last-child:not(:first-child) {
-    border-bottom-left-radius: $btn-border-radius-base;
+    border-bottom-left-radius: $btn-border-radius;
     @include border-top-radius(0);
   }
 }

scss/_buttons.scss

@@ -17,7 +17,7 @@
   cursor: pointer;
   user-select: none;
   border: $border-width solid transparent;
-  @include button-size($padding-base-y, $padding-base-x, $font-size-base, $line-height-base, $btn-border-radius-base);
+  @include button-size($padding-base-y, $padding-base-x, $font-size-base, $line-height-base, $btn-border-radius);
   transition: all .2s ease-in-out;
 
   &,

scss/_code.scss

@@ -17,7 +17,7 @@ code {
   font-size: 90%;
   color: $code-color;
   background-color: $code-bg;
-  @include border-radius($border-radius-base);
+  @include border-radius($border-radius);
 }
 
 // User input typically entered via keyboard

scss/_dropdown.scss

@@ -18,9 +18,9 @@
     margin-left: .25rem;
     vertical-align: middle;
     content: "";
-    border-top: $caret-width-base solid;
-    border-right: $caret-width-base solid transparent;
-    border-left: $caret-width-base solid transparent;
+    border-top: $caret-width solid;
+    border-right: $caret-width solid transparent;
+    border-left: $caret-width solid transparent;
   }
 
   // Prevent the focus on the dropdown toggle when closing dropdowns
@@ -46,7 +46,7 @@
   background-color: $dropdown-bg;
   background-clip: padding-box;
   border: 1px solid $dropdown-border;
-  @include border-radius($border-radius-base);
+  @include border-radius($border-radius);
   @include box-shadow(0 6px 12px rgba(0,0,0,.175));
 
   // Dividers (basically an hr) within the dropdown
@@ -173,7 +173,7 @@
   .caret {
     content: "";
     border-top: 0;
-    border-bottom: $caret-width-base solid;
+    border-bottom: $caret-width solid;
   }
 
   // Different positioning for bottom up menu

scss/_forms.scss

@@ -11,7 +11,7 @@
   display: block;
   width: 100%;
   // // Make inputs at least the height of their button counterpart (base line-height + padding + border)
-  // height: $input-height-base;
+  // height: $input-height;
   padding: $padding-base-y $padding-base-x;
   font-size: $font-size-base;
   line-height: $line-height-base;
@@ -30,7 +30,7 @@
   // &:not(textarea),
   // &:not(select[size]),
   // &:not(select[multiple]) {
-  //   height: $input-height-base;
+  //   height: $input-height;
   // }
 
   // Unstyle the caret on `<select>`s in IE10+.
@@ -103,7 +103,7 @@
   input[type="datetime-local"],
   input[type="month"] {
     &.form-control {
-      line-height: $input-height-base;
+      line-height: $input-height;
     }
 
     &.input-sm,
@@ -125,7 +125,7 @@
 // horizontal form layout.
 
 .form-control-static {
-  min-height: $input-height-base;
+  min-height: $input-height;
   // Size it appropriately next to real form controls
   padding-top: ($padding-base-y + $border-width);
   padding-bottom: ($padding-base-y + $border-width);
@@ -273,7 +273,7 @@ input[type="checkbox"] {
 
   // Ensure icons don't overlap text
   .form-control {
-    padding-right: ($input-height-base * 1.25);
+    padding-right: ($input-height * 1.25);
   }
 }
 // Feedback icon
@@ -283,9 +283,9 @@ input[type="checkbox"] {
   right: 0;
   z-index: 2; // Ensure icon is above input groups
   display: block;
-  width: $input-height-base;
-  height: $input-height-base;
-  line-height: $input-height-base;
+  width: $input-height;
+  height: $input-height;
+  line-height: $input-height;
   text-align: center;
   pointer-events: none;
 }

scss/_input-group.scss

@@ -93,7 +93,7 @@
   text-align: center;
   background-color: $input-group-addon-bg;
   border: 1px solid $input-group-addon-border-color;
-  @include border-radius($border-radius-base);
+  @include border-radius($border-radius);
 
   // Sizing
   &.form-control-sm {

scss/_mixins.scss

@@ -5,7 +5,7 @@
 //
 // Used in conjunction with global variables to enable certain theme features.
 
-@mixin border-radius($radius: $border-radius-base) {
+@mixin border-radius($radius: $border-radius) {
   @if $enable-rounded {
     border-radius: $radius;
   }

scss/_nav.scss

@@ -63,7 +63,7 @@
   .nav-link {
     display: block;
     border: 1px solid transparent;
-    @include border-radius($border-radius-base $border-radius-base 0 0);
+    @include border-radius($border-radius $border-radius 0 0);
 
     @include hover-focus {
       border-color: $nav-tabs-link-hover-border-color $nav-tabs-link-hover-border-color $nav-tabs-border-color;

scss/_pagination.scss

@@ -29,13 +29,13 @@
       > a,
       > span {
         margin-left: 0;
-        @include border-left-radius($border-radius-base);
+        @include border-left-radius($border-radius);
       }
     }
     &:last-child {
       > a,
       > span {
-        @include border-right-radius($border-radius-base);
+        @include border-right-radius($border-radius);
       }
     }
   }

scss/_progress.scss

@@ -33,7 +33,7 @@
 }
 .progress[value]::-webkit-progress-bar {
   background-color: #eee;
-  @include border-radius($border-radius-base);
+  @include border-radius($border-radius);
   @include box-shadow(inset 0 .1rem .1rem rgba(0,0,0,.1));
 }
 .progress[value]::-webkit-progress-value::before {
@@ -41,12 +41,12 @@
 }
 .progress[value]::-webkit-progress-value {
   background-color: #0074d9;
-  border-top-left-radius: $border-radius-base;
-  border-bottom-left-radius: $border-radius-base;
+  border-top-left-radius: $border-radius;
+  border-bottom-left-radius: $border-radius;
 }
 .progress[value="100"]::-webkit-progress-value {
-  border-top-right-radius: $border-radius-base;
-  border-bottom-right-radius: $border-radius-base;
+  border-top-right-radius: $border-radius;
+  border-bottom-right-radius: $border-radius;
 }
 
 // Firefox styles must be entirely separate or it busts Webkit styles.
@@ -56,13 +56,13 @@
 // $-moz-document url-prefix() {
 //   .progress[value] {
 //     background-color: #eee;
-//     .border-radius($border-radius-base);
+//     .border-radius($border-radius);
 //     .box-shadow(inset 0 .1rem .1rem rgba(0,0,0,.1));
 //   }
 //   .progress[value]::-moz-progress-bar {
 //     background-color: #0074d9;
-//     border-top-left-radius: $border-radius-base;
-//     border-bottom-left-radius: $border-radius-base;
+//     border-top-left-radius: $border-radius;
+//     border-bottom-left-radius: $border-radius;
 //   }
 //   .progress[value="0"]::-moz-progress-bar {
 //     color: $gray-light;
@@ -71,8 +71,8 @@
 //     background-image: none;
 //   }
 //   .progress[value="100"]::-moz-progress-bar {
-//     border-top-right-radius: $border-radius-base;
-//     border-bottom-right-radius: $border-radius-base;
+//     border-top-right-radius: $border-radius;
+//     border-bottom-right-radius: $border-radius;
 //   }
 // }
 
@@ -80,7 +80,7 @@
 @media screen and (min-width:0\0) {
   .progress {
     background-color: #eee;
-    @include border-radius($border-radius-base);
+    @include border-radius($border-radius);
     @include box-shadow(inset 0 .1rem .1rem rgba(0,0,0,.1));
   }
   .progress-bar {
@@ -88,8 +88,8 @@
     height: $spacer-y;
     text-indent: -999rem; // Simulate hiding of value as in native `<progress>`
     background-color: #0074d9;
-    border-top-left-radius: $border-radius-base;
-    border-bottom-left-radius: $border-radius-base;
+    border-top-left-radius: $border-radius;
+    border-bottom-left-radius: $border-radius;
   }
   .progress[width^="0"] {
     min-width: 2rem;
@@ -98,8 +98,8 @@
     background-image: none;
   }
   .progress[width="100%"] {
-    border-top-right-radius: $border-radius-base;
-    border-bottom-right-radius: $border-radius-base;
+    border-top-right-radius: $border-radius;
+    border-bottom-right-radius: $border-radius;
   }
 }
 

scss/_tooltip.scss

@@ -77,7 +77,7 @@
   color: $tooltip-color;
   text-align: center;
   background-color: $tooltip-bg;
-  @include border-radius($border-radius-base);
+  @include border-radius($border-radius);
 }
 
 // Arrows

scss/_variables.scss

@@ -81,7 +81,7 @@ $font-size-h4:               1.5rem !default;
 $font-size-h5:               1.25rem !default;
 $font-size-h6:               1rem !default;
 
-$line-height-base:           1.5 !default;
+$line-height:           1.5 !default;
 
 // TODO: nuke this
 $line-height-computed:       1 !default;
@@ -111,15 +111,15 @@ $padding-xs-x:     .5rem !default;
 $line-height-lg:         (4/3) !default;
 $line-height-sm:         1.5 !default;
 
-$border-radius-base:        .25rem !default;
+$border-radius:        .25rem !default;
 $border-radius-lg:       .3rem !default;
 $border-radius-sm:       .2rem !default;
 
 $component-active-color:    #fff !default;
 $component-active-bg:       $brand-primary !default;
 
-$caret-width-base:          .3em !default;
-$caret-width-lg:         $caret-width-base !default;
+$caret-width:          .3em !default;
+$caret-width-lg:         $caret-width !default;
 
 
 // Tables
@@ -170,7 +170,7 @@ $btn-danger-border:              darken($btn-danger-bg, 5%) !default;
 $btn-link-disabled-color:        $gray-light !default;
 
 // Allows for customizing button radius independently from global border radius
-$btn-border-radius-base:         $border-radius-base;
+$btn-border-radius:         $border-radius;
 $btn-border-radius-lg:           $border-radius-lg;
 $btn-border-radius-sm:           $border-radius-sm;
 
@@ -183,8 +183,7 @@ $input-bg-disabled:              $gray-lighter !default;
 $input-color:                    $gray !default;
 $input-border:                   #ccc !default;
 
-// TODO: Rename `$input-border-radius` to `$input-border-radius-base` in v4
-$input-border-radius:            $border-radius-base !default;
+$input-border-radius:            $border-radius !default;
 $input-border-radius-lg:         $border-radius-lg !default;
 $input-border-radius-sm:         $border-radius-sm !default;
 
@@ -193,7 +192,7 @@ $input-box-shadow-focus:         rgba(102,175,233,.6) !default;
 
 $input-color-placeholder:        #999 !default;
 
-$input-height-base:              (($font-size-base * $line-height-base) + ($padding-base-y * 2) + ($border-width * 2)) !default;
+$input-height:              (($font-size-base * $line-height-base) + ($padding-base-y * 2) + ($border-width * 2)) !default;
 $input-height-lg:                (($font-size-lg * $line-height-lg) + ($padding-lg-y * 2) + ($border-width * 2)) !default;
 $input-height-sm:                (($font-size-sm * $line-height-sm) + ($padding-sm-y * 2) + ($border-width * 2)) !default;
 
@@ -288,7 +287,7 @@ $container-max-widths: (
 // Basics of a navbar
 // $navbar-height:                    50px !default;
 $navbar-margin-bottom:             $line-height-computed !default;
-$navbar-border-radius:             $border-radius-base !default;
+$navbar-border-radius:             $border-radius !default;
 $navbar-padding-horizontal:        $spacer !default;
 $navbar-padding-vertical:          ($spacer / 2) !default;
 $navbar-collapse-max-height:       340px !default;
@@ -355,7 +354,7 @@ $nav-tabs-active-link-hover-border-color:   #ddd !default;
 $nav-tabs-justified-link-border-color:            #ddd !default;
 $nav-tabs-justified-active-link-border-color:     $body-bg !default;
 
-$nav-pills-border-radius:                   $border-radius-base !default;
+$nav-pills-border-radius:                   $border-radius !default;
 $nav-pills-active-link-hover-bg:            $component-active-bg !default;
 $nav-pills-active-link-hover-color:         $component-active-color !default;
 
@@ -491,7 +490,7 @@ $modal-sm:                    300px !default;
 // Define alert colors, border radius, and padding.
 
 $alert-padding:               15px !default;
-$alert-border-radius:         $border-radius-base !default;
+$alert-border-radius:         $border-radius !default;
 $alert-link-font-weight:      bold !default;
 
 $alert-success-bg:            $state-success-bg !default;
@@ -515,7 +514,7 @@ $alert-danger-border:         $state-danger-border !default;
 
 $progress-bg:                 #f5f5f5 !default;
 $progress-bar-color:          #fff !default;
-$progress-border-radius:      $border-radius-base !default;
+$progress-border-radius:      $border-radius !default;
 
 $progress-bar-bg:             $brand-primary !default;
 $progress-bar-success-bg:     $brand-success !default;
@@ -528,7 +527,7 @@ $progress-bar-info-bg:        $brand-info !default;
 
 $list-group-bg:                 #fff !default;
 $list-group-border:             #ddd !default;
-$list-group-border-radius:      $border-radius-base !default;
+$list-group-border-radius:      $border-radius !default;
 
 $list-group-hover-bg:           #f5f5f5 !default;
 $list-group-active-color:       $component-active-color !default;
@@ -550,7 +549,7 @@ $list-group-link-heading-color: #333 !default;
 $thumbnail-padding:           .25rem !default;
 $thumbnail-bg:                $body-bg !default;
 $thumbnail-border:            #ddd !default;
-$thumbnail-border-radius:     $border-radius-base !default;
+$thumbnail-border-radius:     $border-radius !default;
 
 
 // Badges