Later vs Latter: Time or the Second of Two?

Later is about time. Latter is about reference. The spelling difference is small, but the words do different grammatical work.

We can discuss it later. / We considered speed and accuracy; the latter mattered more.

Latter needs a clear pair

Traditional usage reserves the latter for the second of two items. If you have listed four possibilities, name the item instead.

This is partly a cohesion issue: reference words should reduce processing effort. The same principle appears in unclear pronoun reference. Do not confuse latter with latest, which means “most recent.”

Prefer explicit reference when the text is dense

Even when the former and the latter are grammatically possible, repeating the key noun may be clearer in technical prose. Readers should not have to scan backwards to recover a pair. Precision sometimes means choosing a slightly longer phrase.