week-old; age in weeks
Used as a noun meaning 'age measured in weeks', or as a suffix attached to a number to indicate the age of a young animal or infant in weeks. Common in veterinary, pediatric, and developmental contexts.
This puppy is only 3 weeks old.
Check the developmental stages by week of age.
Means 'age in days', used for very young newborns or animals. 週齢 is a coarser measure.
Standard kanji form. 週 means 'week', 齢 means 'age'.
Variant using 令 (command, order) as a simpler substitute for 齢. Less common but encountered.
Compound of 週 (shū, 'week') + 齢 (rei, 'age'). A straightforward Sino-Japanese term.