/* Keyword values */
transform: none;

/* Function values */
transform: matrix(1, 2, 3, 4, 5, 6);
transform: translate(12px, 50%);
transform: translateX(2em);
transform: translateY(3in);
transform: scale(2, 0.5);
transform: scaleX(2);
transform: scaleY(0.5);
transform: rotate(0.5turn);
transform: skew(30deg, 20deg);
transform: skewX(30deg);
transform: skewY(1.07rad);
transform: matrix3d(1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16);
transform: translate3d(12px, 50%, 3em);
transform: translateZ(2px);
transform: scale3d(2.5, 1.2, 0.3);
transform: scaleZ(0.3);
transform: rotate3d(1, 2, 3, 10deg);
transform: rotateX(10deg);
transform: rotateY(10deg);
transform: rotateZ(10deg);
transform: perspective(17px);

/* Multiple function values */
transform: translateX(10px) rotate(10deg) translateY(5px);

/* Global values */
transform: inherit;
transform: initial;
transform: unset;

<style>
   .box {
     width: 200px;
     height: 200px;
     line-height: 200px;
     border: 1px solid green;

     text-align: center;
     margin: 0 auto;
   }

   .box + .box {
     margin-top: 100px;
   }

   .rotate {
     transform: rotate(45deg);
   }
 </style>

 <div class="box">正常元素</div>

 <div class="box rotate">旋转45deg</div>

.rotate {
  transition: transform 0.5s ease-in-out;
}

.rotate:hover {
  transform: rotate(45deg);
}

.rotate {
 animation: rotate-ani 2s linear infinite;
}

@keyframes rotate-ani {
 from {
   transform: rotate(0deg);
 }
 to {
   transform: rotate(360deg);
 }
}