A young dog, typically under one year old. The most common meaning.
A puppy is playing in the garden.
She started keeping a puppy.
small dog
A dog of small breed or size, not necessarily young. Less common than the 'puppy' sense.
That small dog is already an adult, but it's very tiny.
I've been keeping a puppy since last year.
Last week, our dog had puppies.
I found an abandoned puppy in the park.
She ran up to me like an excited puppy.
犬 is the general word for 'dog' of any age or size, while 子犬 specifically means a young puppy (or a small dog).
counter for small animals · counter for rolls of cloth · archaic counter for horses · roll of cloth
puppy mill; puppy farm
Standard and most common spelling.
Alternative kanji spelling; 仔 specifically means 'young animal'.
Less common spelling; 小 means 'small'.
Search-only form; not a standard written spelling.
Compound of 子 (こ, 'child') + 犬 (いぬ, 'dog'). The reading こいぬ is a straightforward combination of the kun'yomi readings of the two kanji.