Modifying tag parameters

Could someone tell me what message below means and how to correct it please.

Parse error: syntax error, unexpected T_CONSTANT_ENCAPSED_STRING, expecting ‘)’ in
.com/wp-content/themes/andrea/page.php on line 19
‘title_li’ => _(‘Pages’),

Line 19 reads: ‘title_li’ => _(‘Pages’),

Would be very grateful for any advice on how to correct it. I did want to change the code so tab menus would appear.

Cathy