Remove Item from an Array in Power Shell

Hello Guys i have a simple but driving my crazy question:

in power shell i did the following

$a = 1,2,3,4

$a

1

2

3

4

now the question is: if i want to Remove number 3 for example from that array, how can i do that >?????

i tried

$a - 3 " didnt work"

any ideas?