a

A (as a label or placeholder), A (a top grade)

→ a
noun Rare #37,985
A (as a label or placeholder) Often used to stand for an unspecified person, place, or thing, or as the label for one of several choices.
JA: aとbのどちらが好きですか。
EN: Which do you like better, A or B?
A (a top grade) In Japan, A is a high grade.
JA: テストでaを取りました。
EN: I got an A on the test.

AとBの違いは何ですか。

What is the difference between A and B?

Aは十分にあるがBは足りない。

There is enough A, but not enough B.

A:父上は生きている

A: Father is alive.

— 灼熱の魂 (2010)

Aはアルファベットの最初の文字だ。

A is the first letter of the alphabet.

A市からB市までどれくらいの時間がかかりますか。

How long does it take to get from City A to City B?