Formal/literary question word or conjunctive adverb meaning 'how much/many' or 'however much'. In modern Japanese, どのくらい or どれほど are more common in speech; いかほど is often used in polite or written contexts.
Similar in meaning and formality to いかほど, but slightly more common in modern writing.
Etymology
Compound of いか (how) + ほど (extent, degree). The exact derivation of いか is uncertain, but it is related to the interrogative root ika- seen in いかに and いかなる.
