noun
Refers to how something or someone looks or seems, often used in set phrases like 体をなす (to take shape) or 体よく (plausibly, with a good appearance).
彼の話はどうも体をなしていない。
His story doesn't really hold together.
体よく断られた。
I was politely turned down.
体裁 is a more common word for outward appearance or form, while 体 (てい) is often used in fixed expressions.
From Middle Chinese 體 (appearance, form). The reading てい is the on'yomi.