Can I use shorthand margin syntax to change just left and right values?

Question

Can I use the shorthand margin syntax if I want to add margin-left: auto and margin-right: auto while leaving the margin-top and margin-bottom alone?

The basic idea:

.center {
    margin: dont-specify auto;
}

Thanks!

Edit: In short, the answer is that there is no such keyword. For clarity, by 'dont-specify', I did not mean 'remove-specification', 'roll-back-specification' or 'specify-with-lower-specificity'. I meant, 'this rule should not specify a new value'. I take responsibility for being unclear. It is indeed very easy to interpret 'dont-specify' a multitude of different ways! Thanks for everyone's answers!

Answer 1

Not in shorthand no. Possible values are:

margin:10px; // top/right/bottom/left
margin:10px 10px; // top/bottom left/right
margin:10px 10px 10px; // top right/left bottom
margin:10px 10px 10px 10px; // top right bottom left

Answer 2

OP comment

If the element being styled has margin-top: 20px and margin-bottom: 10px at the moment, won't using "auto", overwrite that?

A: yes you can, It all depends on your specificity.

Snippet

body {
  margin: 0
}
main {
  border: solid green
}
div,
span,
article,
section {
  display: block; /* needed for span */
  margin-left: 20px;
  margin-right: 10px;
  width: 100px;
  height: 100px;
  border: dashed red 1px
}
/* override margin-left/right */
[class*="class-"] {
  margin: auto; /* shorthand for top right bottom left - or - top/bottom right/left */
}

<main>
  <span class="class-1"></span>
  <div class="class-2"></div>
  <article class="class-3"></article>
  <section class="class-4"></section>
</main>