Quasi - As if
Quater in die (Q.I.D) - Take four times a day
Quem di diligunt, adolescens moritur - Whom the gods love die young. (only the good die young)

Quemadmodum possums scire utrum vere simus an solum sentiamus nos esse?

How are we to know whether we actually exist or only think we exist?

Quemadmoeum gladis nemeinum occidit, occidentis telum est - A sword is never a killer, it's a tool in the killer's hands. (Seneca)
Qui bene cantat, bis orat - He who sings well, prays twice
Qui bono? - Who benfits?
Qui dedit benificium taceat; narret qui accepit - Let him who has done a good deed be silent; let him who has received it tell it. (Seneca)
Qui desiderat pacem, praeparet bellum - Let him who wishes for peace prepare for war. (Vegetius)
Qui docet discit - He who teaches learns