even if / although, even though

if only, I wish, from your lips to God's ears

as if; as though (as to suggest that)

(now archaic or literary) certainly, yes (indeed), but of course (used to contradict a negative assertion)

if, in case

youth is wasted on the young, you can't put an old head on young shoulders (it's too bad that young people lack the experience and wisdom which only come with age; likewise, it's a pity that old people lack the physical wherewithal to take full advantage of their experience and wisdom)

(informal) to pretend, to do as if

if need be

except, if not

(informal) not so fast! hold your horses!