Round towards zero

Python 3, 3 bytes

int

Try it online!

Truncates the digits after the decimal point.

NOTE: This is a trivial answer. Please take a look at the other answers before upvoting

Python 2, 3 bytes

int

Try it online!

Perl 5 -p056l15, 2 bytes

<>

Try it online!

How does that work?

-056   # (CLI) Make "." the input record separator
-l15   # (CLI) Make "\n" the output record separator
       # (otherwise it would use the input separator)
-p     # (CLI) Implicitly read $_ from STDIN
<>     # Read the second input field and do nothing with it
-p     # (CLI) Output $_ to STDOUT

Or if you prefer a more traditional answer:

Perl 5, 6 bytes

$_=int

Try it online!