脇: beside a chair and the underarm of a shirt
Compare a bag beside a chair with the wet underarm area of a shirt after running, using the reference object to identify the sense of 脇.
A position beside the chair
脇 (わき) can identify a position beside an object. 椅子の脇 gives the chair as the reference for where the bag was placed.
“鞄は通路を塞がないよう椅子の脇に置いた。” says that the bag was placed beside the chair so that it would not block the aisle. 通路を塞がないよう states the purpose of the placement, separate from the completed act of placing it.
The underarm area of the shirt
脇 can also refer to an armpit or the corresponding area of clothing. In シャツの脇, identify the part of the shirt corresponding to that body area.
“走った後、シャツの脇まで汗でぬれていた。” says that after running, even the underarm area of the shirt was wet with sweat. Keep both the past state of being wet and the extent expressed by まで.
Read the reference and the extent together
The chair’s 脇 is a position beside it; the shirt’s 脇 is a particular area of the garment. The preceding chair or shirt helps distinguish the two senses of the same word.
The wet underarm area does not by itself establish the state of the entire shirt. Likewise, the purpose of not blocking the aisle should not be treated as a reported check of the actual aisle conditions.
What provides the reference for 脇 in the bag sentence and in the shirt sentence?
Show the answer and why
The bag sentence uses the chair to locate a position beside it. The shirt sentence identifies the garment’s underarm area, which was wet with sweat after running; it does not establish the state of the entire shirt.