| Present "constrain" | I | constrain | |
| Present Continuous "constrain" | I | am constraining | |
| Simple past "constrain" | I | constrained | |
| Past Continuous "constrain" | I | was constraining | |
| Present perfect "constrain" | I | have constrained | |
| Present perfect continuous "constrain" | I | have been constraining | |
| Past perfect "constrain" | I | had constrained | |
| Past perfect continuous "constrain" | I | had been constraining | |
| Future "constrain" | I | will constrain | |
| Future continuous "constrain" | I | will be constraining | |
| Future perfect "constrain" | I | will have constrained | |
| Future perfect continuous "constrain" | I | will have been constraining |