| Simple | Progressive | Perfect | Progressive |
| Present |
| I slacken |
| you slacken |
| he/she/it slackens |
| we slacken |
| you all slacken |
| they slacken |
|
| I am slackening |
| you are slackening |
| he/she/it is slackening |
| we are slackening |
| you all are slackening |
| they are slackening |
|
| I have slackened |
| you have slackened |
| he/she/it has slackened |
| we have slackened |
| you all have slackened |
| they have slackened |
|
| I have been slackening |
| you have been slackening |
| he/she/it has been slackening |
| we have been slackening |
| you all have been slackening |
| they have been slackening |
|
| Past |
| I slackened |
| you slackened |
| he/she/it slackened |
| we slackened |
| you all slackened |
| they slackened |
|
| I was slackening |
| you were slackening |
| he/she/it was slackening |
| we were slackening |
| you all were slackening |
| they were slackening |
|
| I had slackened |
| you had slackened |
| he/she/it had slackened |
| we had slackened |
| you all had slackened |
| they had slackened |
|
| I had been slackening |
| you had been slackening |
| he/she/it had been slackening |
| we had been slackening |
| you all had been slackening |
| they had been slackening |
|
| Future |
| I will slacken |
| you will slacken |
| he/she/it will slacken |
| we will slacken |
| you all will slacken |
| they will slacken |
|
| I will be slackening |
| you will be slackening |
| he/she/it will be slackening |
| we are slackening |
| you all will be slackening |
| they will be slackening |
|
| I will have slackened |
| you will have slackened |
| he/she/it will have slackened |
| we will have slackened |
| you all will have slackened |
| they will have slackened |
|
| I will have been slackening |
| you will have been slackening |
| he/she/it will have been slackening |
| we will have been slackening |
| you all will have been slackening |
| they will have been slackening |
|
