adverb
Adverbial use indicating that something has happened sooner than expected or by the current moment. Often used in expressions like 早くも.
早くも桜が咲き始めた。
The cherry blossoms have already started blooming.
彼は早くも帰ってしまった。
He has already gone home.
noun, used as a prefix, noun, used as a suffix, noun
Used as a prefix, suffix, or standalone noun to indicate speed or earliness. Common in compounds like 早口 (fast speech) or 早起き (early rising).
早口で話さないでください。
Please don't speak quickly.
明日は早いので、もう寝ます。
I have an early start tomorrow, so I'm going to bed now.
速い emphasizes physical speed, while 早い (and this word's 早) emphasizes earliness or quickness in time.
もう is the standard word for 'already'; 早 is a more literary or compound-bound alternative.
The kanji 早 is a pictograph of the sun rising, representing the concept of early morning and by extension quickness or earliness. The reading はや is native Japanese.