colleague plural
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Colleague is singular both plural and singular singular plural plural singular both plural and singular plural both plural and singular .
The CEO’s salary (one CEO)
The MPs’ staff (the staff supporting more than one MP)
BizWritingTip response: If you want to make capital letters and abbreviations ending in a capital letter plural , it is best to just add a lowercase s*
References:
http://ontariotraining.net/grammar-tip-plurals-with-abbreviations/
http://spcollege.libguides.com/c.php?g=254288&p=1695256