彼を招待するべきだったのにしなかった。
tbd
You should have invited him, but you didn't.
You ought to have invited him, but you didn't.
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を
1. indicates direct object of action
2. indicates subject of causative expression
3. indicates an area traversed
4. indicates time (period) over which action takes place
5. indicates point of departure or separation of action
6. indicates object of d...
表示动作的直接对象；表示经过的场所；表示离开或分开的点
の
1. indicates possessive
2. nominalizes verbs and adjectives
3. substitutes for "ga" in subordinate phrases
4. (at sentence-end, falling tone) indicates a confident conclusion
5. (at sentence-end) indicates emotional emphasis
6. (at sentence-end, risi...
句尾起强调作用；助词，表示所有关系
に
1. at (place, time), in, on, during
2. to (direction, state), toward, into
3. for (purpose)
4. because of (reason), for, with
5. by, from
6. as (i.e. in the role of)
7. per, in, for, a (e.g. "once a month")
8. and, in addition to
9. if, although
tbd