diff --git a/src/transition/schedule.js b/src/transition/schedule.js
index f1385be..0e8c0d1 100644
--- a/src/transition/schedule.js
+++ b/src/transition/schedule.js
@@ -2,7 +2,7 @@ import {dispatch} from "d3-dispatch";
 import {timer, timeout} from "d3-timer";
 
 var emptyOn = dispatch("start", "end", "interrupt");
-var emptyTweens = [];
+var emptyTween = [];
 
 var CREATED = 0,
     SCHEDULED = 1,
@@ -17,7 +17,7 @@ export default function(node, key, id, index, group, timing) {
     index: index, // For context during callback.
     group: group, // For context during callback.
     on: emptyOn,
-    tweens: emptyTweens,
+    tween: emptyTween,
     time: timing.time,
     delay: timing.delay,
     duration: timing.duration,
@@ -56,7 +56,7 @@ export function get(node, key, id) {
 
 function start(node, key, self) {
   var schedules = node[key],
-      tweens;
+      tween;
 
   // Initialize the self timer when the transition is created.
   // Note the actual delay is not known until the first callback!
@@ -108,18 +108,18 @@ function start(node, key, self) {
     });
 
     // Dispatch the start event.
-    // Note this must be done before the tweens are initialized.
+    // Note this must be done before the tween are initialized.
     self.on.call("start", node, node.__data__, self.index, self.group);
     self.state = STARTED;
 
-    // Initialize the tweens, deleting null tweens.
-    tweens = new Array(n = self.tweens.length);
+    // Initialize the tween, deleting null tween.
+    tween = new Array(n = self.tween.length);
     for (i = 0, j = -1; i < n; ++i) {
-      if (o = self.tweens[i].value.call(node, node.__data__, self.index, self.group)) {
-        tweens[++j] = o;
+      if (o = self.tween[i].value.call(node, node.__data__, self.index, self.group)) {
+        tween[++j] = o;
       }
     }
-    tweens.length = j + 1;
+    tween.length = j + 1;
   }
 
   function tick(elapsed) {
@@ -127,8 +127,8 @@ function start(node, key, self) {
         e = t >= 1 ? 1 : self.ease.call(null, t),
         i, n;
 
-    for (i = 0, n = tweens.length; i < n; ++i) {
-      tweens[i].call(null, e);
+    for (i = 0, n = tween.length; i < n; ++i) {
+      tween[i].call(null, e);
     }
 
     // Dispatch the end event.
diff --git a/src/transition/tween.js b/src/transition/tween.js
index a25cc8a..bc2d4cd 100644
--- a/src/transition/tween.js
+++ b/src/transition/tween.js
@@ -1,26 +1,26 @@
 import {get, set} from "./schedule";
 
 function tweenFunction(key, id, name, value) {
-  var tweens0, tweens1;
+  var tween0, tween1;
   return function() {
     var schedule = set(this, key, id),
-        tweens = schedule.tweens;
+        tween = schedule.tween;
 
-    // If this node shared tweens with the previous node,
-    // just assign the updated shared tweens and we’re done!
+    // If this node shared tween with the previous node,
+    // just assign the updated shared tween and we’re done!
     // Otherwise, copy-on-write.
-    if (tweens !== tweens0) {
-      tweens1 = (tweens0 = tweens).slice();
-      for (var t = {name: name, value: value}, i = 0, n = tweens1.length; i < n; ++i) {
-        if (tweens1[i].name === name) {
-          tweens1[i] = t;
+    if (tween !== tween0) {
+      tween1 = (tween0 = tween).slice();
+      for (var t = {name: name, value: value}, i = 0, n = tween1.length; i < n; ++i) {
+        if (tween1[i].name === name) {
+          tween1[i] = t;
           break;
         }
       }
-      if (i === n) tweens1.push(t);
+      if (i === n) tween1.push(t);
     }
 
-    schedule.tweens = tweens1;
+    schedule.tween = tween1;
   };
 }
 
@@ -31,9 +31,9 @@ export default function(name, value) {
   name += "";
 
   if (arguments.length < 2) {
-    var tweens = get(this.node(), key, id).tweens;
-    for (var i = 0, n = tweens.length, t; i < n; ++i) {
-      if ((t = tweens[i]).name === name) {
+    var tween = get(this.node(), key, id).tween;
+    for (var i = 0, n = tween.length, t; i < n; ++i) {
+      if ((t = tween[i]).name === name) {
         return t.value;
       }
     }
@@ -50,10 +50,10 @@ export function tweenValue(transition, name, value) {
 
   transition.each(function() {
     var schedule = set(this, key, id), v = value.apply(this, arguments);
-    (schedule.values || (schedule.values = {}))[name] = v == null ? null : v + "";
+    (schedule.value || (schedule.value = {}))[name] = v == null ? null : v + "";
   });
 
   return function(node) {
-    return get(node, key, id).values[name];
+    return get(node, key, id).value[name];
   };
 }