There are 18 words that start with 'loos'.
| loos | loose | loosed |
| loosen | looser | looses |
| loosely | loosens | loosest |
| loosing | loosened | loosener |
| looseners | looseness | loosening |
| loosenesses | loosestrife | loosestrifes |
Note: These 18 words that start with 'loos' are found from the USA & Canada version of the tournament Scrabble word list.