TSUMUGU · TOCFL 2 (est.) · 字
於
ㄩˊ · yú
prep — at, in, to
字源 FORM — what the parts do
於形a worn variant of 烏, the crow
The same bird as 烏 the crow — one graph in two ways of writing, until this one was hired out as the empty joint of the sentence: at, in, to. 於是 thereupon, 由於 owing to, 對於 toward, 終於 at last.
意 · Meanings
(本義)烏（本同一字）— the crow — one graph with 烏 before the split
(假借)在、到（介詞）— at, in, to — the joint word常用
→對於、關於— toward, regarding
→終於、於是— at last; thereupon常用
(本義) original meaning · → ⇒ each arrow = one more step of extension