Rashi on Genesis 37:31/רש"י על בראשית ל״ז:ל״א

1שעיר עזים A KID OF THE GOATS — its blood resembles that of a human being (Genesis Rabbah 84:19).

2הַכֻּתֹּנֶת THE COAT — This is the form of the noun in the absolute state, but when it is in the construct state — as e.g., Joseph’s coat”, “the coat of many colours”, “the coat of linen”, — it is punctuated as כְּתֹנֶת.