A reaches the same degree of a quality as a known yardstick B.
序 · The move
1Put the thing being sized up in A and the yardstick in B.Is B a known size the listener can picture?
2Set 這麼 for a yardstick close at hand, 那麼 for one further off.Near speaker → 這麼; away → 那麼.
3End on the quality word (大, 高, 重…), no 很 in front.Did a stray 很 sneak in before the adjective?
例 · Examples
1這間this (+ measure 間 for rooms)教室classroom有reaches the extent of一個籃球場a basketball court這麼this much大big。
This classroom is as big as a basketball court.
界 · Boundary
A比B…
有 says A reaches B's level (A is as X as B). 比 says A passes B's level (A is more X than B). 有 matches; 比 beats.
A跟B一樣…
一樣 declares A and B equal outright. 有 measures A up against B as a yardstick, and often runs in a question or a 沒 negative (沒有B那麼大 = does not reach B's size).
✗ 這間教室有一個籃球場這麼很大。 → ✓ 這間教室有一個籃球場這麼大。
✗ 他有他哥哥比高。 → ✓ 他有他哥哥那麼高。
✗ 這本書沒有那本那麼貴。 (claiming A reaches B) → ✓ 這本書有那本那麼貴。 (沒有 only when A falls short of B)
English "as big as" maps the quality between two "as"; Mandarin puts the yardstick B after 有 and the quality last, with no word before 大.