A2
ている — in progress, and still true
How the Japanese ている form marks both an action in progress and a continuing state, and why 知っている and 住んでいる are never said any other way.
て plus いる. The commonest form in spoken Japanese, and it covers two things English keeps apart.
An action in progress
今、食べています。
Ima, tabete imasu.
I’m eating right now.
雨が降っています。
Ame ga futte imasu.
It’s raining.
This much matches the English -ing and needs no explanation.
A state that resulted from an action
The second meaning is the one to learn deliberately. With verbs that describe a change, ている marks the state left behind — not the change happening.
東京に住んでいます。
Tōkyō ni sunde imasu.
I live in Tokyo.
結婚しています。
Kekkon shite imasu.
I’m married.
この店は閉まっています。
Kono mise wa shimatte imasu.
This shop is closed.
結婚しています is not I am getting married. The marrying happened; the state continues. Same for 閉まっています — the shop shut at some point and is shut now.
Some verbs have no other form
知る is the clearest case. 知っています is I know; the plain 知ります would mean the moment of coming to know, which is almost never what you want.
彼を知ります。
彼を知っています。
知る is the act of finding out. Knowing is the state that follows it, so it takes ている. The negative, though, is 知りません — not 知っていません — which is irregular and worth learning as a pair.
In speech the い disappears
食べてる, 知ってる, 住んでる. The full form is what you write; the short one is what you hear, and it is not sloppy so much as normal.