(ないし)

ないし
conjunction
from... to...; or; possibly even
1. from... to...; through; between
Indicates a range between two values, quantities, or points. Used in formal and written contexts, similar to English 'from X to Y' or 'X through Y'.
(さん)(にち)乃至(ないし)(いつ)()かかる。
It takes three to five days.
参加者(さんかしゃ)(ひゃく)(めい)乃至(ないし)二百(にひゃく)(めい)見込(みこ)みだ。
The expected number of participants is between 100 and 200.
罰金(ばっきん)乃至(ないし)懲役(ちょうえき)(しょ)される。
Punished by a fine or possibly imprisonment.
2. or; possibly even
Used to present an alternative that may be more extreme or unexpected than the first option, similar to 'or even' or 'or possibly'.
数週間(すうしゅうかん)乃至(ないし)(すう)(げつ)かかるかもしれない。
It might take several weeks, or even several months.
停職(ていしょく)乃至(ないし)解雇(かいこ)もありうる。
Suspension, or even dismissal, is possible.
この問題(もんだい)地域(ちいき)社会(しゃかい)乃至(ないし)国全体(くにぜんたい)影響(えいきょう)(およ)ぼす可能性(かのうせい)がある。
This problem could affect the local community, or even the entire nation.

USAGE:
A formal conjunction used primarily in written language, legal documents, and academic texts. Sense 1 (range) is the more common usage. In everyday speech, から(から)まで(まで) or 〜から(から)〜 is preferred for expressing ranges.

COMMON COLLOCATIONS:

  • A乃至(ないし)B (A to/through B)
  • (すう)〜、乃至(ないし)(すう)〜 (several X, or even several Y)

SIMILAR WORDS:

  • から〜まで: from... to... — the everyday equivalent for expressing ranges
  • もしくは: or, alternatively — a formal alternative conjunction without the range meaning
  • あるいは: or, possibly — less formal than 乃至(ないし)