来自PIE*esmi ,是，存在，来自*es, 是，词源同单词is，同词根esse, est, sattva等，见essence, interest, 梵语词Bodhisattva, ( Buddha-to-be, 菩萨）。
英文词源
am (v.)
Old English eom "to be, to remain," (Mercian eam, Northumbrian am), from PIE *esmi- (cognates: Old Norse emi, Gothic im, Hittite esmi, Old Church Slavonic jesmi, Lithuanian esmi), from root *es-, the S-ROOT, which also yielded Greek esti-, Latin est, Sanskrit as-, and German ist.
In Old English it existed only in present tense, all other forms being expressed in the W-BASE (see were, was). This cooperative verb is sometimes referred to by linguists as *es-*wes-. Until the distinction broke down 13c., *es-*wes- tended to express "existence," with beon meaning something closer to "come to be" (see be).
Old English am had two plural forms: 1. sind/sindon, sie and 2. earon/aron The s- form (also used in the subjunctive) fell from use in English in the early 13c. (though it continues in German sind, the 3rd person plural of "to be") and was replaced by forms of be, but aron (aren, arn, are, from Proto-Germanic *ar-, probably a variant of PIE root *es-) continued, and as am and be merged it encroached on some uses that previously had belonged to be. By the early 1500s it had established its place in standard English. Art became archaic in the 1800s.
实用例句
1. I too am committing myself to continue the fight for justice.
我本人也保证将继续为正义而战。来自柯林斯例句
2. They have both behaved very badly and I am very hurt.
他们俩都很不友善，让我非常难过。来自柯林斯例句
3. This, I am sorry to say, is almost entirely wishful thinking.
我很遗憾，这几乎完全是一厢情愿的想法。来自柯林斯例句
4. I am expecting several important letters but nothing has arrived.
