From SRD 5.2.1
Ally
A creature is your ally if it is a member of your adventuring party, your friend, on your side in combat, or a creature that the rules or the DM designates as your ally.
A creature is your ally if it is a member of your adventuring party, your friend, on your side in combat, or a creature that the rules or the DM designates as your ally.
15 of 151 in SRD 5.2.1