I picked up Japanese just recently, and I am confused as to why the word 昨夜 has so many different ways to pronounce it. In my dictionary, the pronunciations are listed as ゆうべ、ゆんべ and さくや. Do the different readings convey the same meaning, or do they mean different things?
Additionally, can someone explain how 昨夜 differs from 前夜?
From what I understand, 「夕{ゆう}べ」typically refers to the evening while 「昨夜」means last night specifically.「さくや」seems to be used in more formal contexts.「ゆんべ」seems more colloquial.
The varying readings are pretty typical in Kanji and they come from historical reasons where Kanji acquired many different Chinese readings. See other questions on readings of kunyomi and onyomi. If you're interested in etymology, this Wiktionary page shows the various origins of 昨夜.
昨夜 is always read さくや in modern standard Japanese. I was not aware of the other readings, and you can safely forget them. According to monolingual dictionaries, ゆうべ seems to be an obsolete reading used in the past. (Some big dictionaries tend to list rare and/or obsolete readings even native speakers do not know. If you often run into this type of problem, you may want to get a smaller dictionary for learners or native elementary school children.)
ゆうべ is written as 夕べ in kanji (and kana) in modern standard Japanese. It also means "last night", but sounds more colloquial. 夕べ also means "night (event)". ゆんべ is highly dialectal or old, so you should not use it.
昨夜 means "last night" and is relative to today. 前夜 means "the night before" or "eve", and is relative to some "main" day. For example クリスマスの前夜 always refers to the 24th of December regardless of the date of today.
