defective verb, only second-person present imperative, no subjunctive or indicative
- Look [at this]! See [this]!
- Take heed, listen
- Watch and learn.
- Pay attention [to someone or something specified]!
- Focus! Concentrate!
- (World Wide Web) Click [here], check [this out]
- Come (a request or invitation to move toward the speaker)
from iej, take notice of, observe