how to identify more than one page in using conditionals

Hi,
I’d like to know the syntax to identify more than one page in order to use a conditional statement;

I’ve used

if (is_page('pagename1'))
{ then do something }

but how would you say

if (is_page('pagename1 or pagename2 or pagename3')) {
then do something }

?
Thanks in advance for any help