adverb (fukushi)nouns which may take the genitive case particle 'no'adjectival nouns or quasi-adjectives (keiyodoshi)word usually written using kana alonea little;a bit;somewhat;slightly;rather
ここだけの話だが、彼はいささか間が抜けている。
Between you and me, he is rather stupid.
Other forms
聊か 【いささか】 (rarely used kanji form) · 些 【いささか】 (irregular okurigana usage) · 聊 【いささか】 (irregular okurigana usage) (rarely used kanji form)