1.
the latter, the second one
The second of two things or people mentioned.
There are two proposals, A and B, but considering cost, the latter is more realistic.
後者 means "the latter" when referring to the second of two items previously mentioned.
Register
Formal/written style. More common in academic writing, business documents, and formal speech.
Common patterns
前者は〜、後者は〜 (The former is ~, the latter is ~)
Common expressions
Similar words
前者 (the former, the first one)
Usage
Only used when exactly two items are being compared. For more than two items, use 最後の or ordinal numbers.