adverb
Used when stating something openly without embellishment or concealment; often with verbs like 言う or 話す.
ありていに言えば、その計画は失敗だった。
Frankly speaking, the plan was a failure.
彼はありていに事情を話した。
He explained the circumstances plainly.
Derived from the classical Japanese adjective ありてい (ari-tei), meaning 'as it is' or 'plain,' combined with the adverbial particle に. The exact historical development is uncertain, but it has been used since the Heian period.