There are 18 words that start with 'cosi'.
| cosie | cosied |
| cosier | cosies |
| cosign | cosily |
| cosine | cosiest |
| cosigns | cosines |
| cosigned | cosigner |
| cosiness | cosigners |
| cosigning | cosinesses |
| cosignatory | cosignatories |
Note: These 18 words that start with 'cosi' are found from the USA & Canada version of the tournament Scrabble word list.