| Present "strengthen" | I | strengthen | |
| Present Continuous "strengthen" | I | am strengthening | |
| Simple past "strengthen" | I | strengthened | |
| Past Continuous "strengthen" | I | was strengthening | |
| Present perfect "strengthen" | I | have strengthened | |
| Present perfect continuous "strengthen" | I | have been strengthening | |
| Past perfect "strengthen" | I | had strengthened | |
| Past perfect continuous "strengthen" | I | had been strengthening | |
| Future "strengthen" | I | will strengthen | |
| Future continuous "strengthen" | I | will be strengthening | |
| Future perfect "strengthen" | I | will have strengthened | |
| Future perfect continuous "strengthen" | I | will have been strengthening |