N5 — outside your level filter
Is said whole, with nothing composed onto it and takes no copula, so there is no paradigm to conjugate.
失礼しました
shitsureishimashitasorry about that; my apologiesN5expression
Related words
Readings and definitions from JMdict, © the Electronic Dictionary Research and Development Group (EDRDG), used under CC BY-SA 4.0; levels from the Tanos JLPT lists.