Questions & Answers about Nein, es ist keine Jacke.
Why do we use keine here instead of nicht?
In English you say "not a", but German has a special word for this: kein (or its forms like keine). You use nicht to negate actions (verbs) or descriptions (adjectives), but to negate a noun that would normally have "a" or "an" in front of it, you always use the negative article keine.
Why does it end in -e (keine)?
The ending changes to match the gender of the noun. Because Jacke is a feminine noun (die Jacke), the negative article adds an -e to become keine. If you were talking about a masculine noun like Pullover (sweater) or a neuter noun like Hemd (shirt), you would just use kein.
If Jacke is feminine, why does the sentence start with es ist instead of sie ist?
In this sentence, es is used as a general "it" to identify something, just like in English ("What is that? It is a jacket."). We use es ist or das ist when pointing something out. You would only use sie (she/it) if you were already talking specifically about the jacket (for example, "Where is the jacket? It is in the closet.").
Is there a trick to remembering that Jacke is feminine?