Suitable > having the qualities that are correct , good,required and needed for something . This book is suitable for kids . ( this book has all the qualities that are good for the kids ) This spicy food is not suitable for kids ( this food doesnt have the QUALITIES that are good for kids This tool is used for farming ( this tool has the quality needed for farming ) Appropriate > having the correctness and BEING PROPER for a particular CIRCUMSTANCE /situation/person This book is appropiate for kids ( this book has contents that are proper and correct for kids to know) These 2 words are interchangeable most time . Find a suitable or appropriate dress for the party > find a dress that has the qualities required for the party or find a dress that is " proper and correct ' for a party . The difference is better illustrated by examples . This machine is suitable for farming , but it is not appropriate to use it now because my grandfather is living with us for a few days , and he hates modern technology > this machines has all the qualities needed for farming , but it is not 'proper or correct ' to use it out of respect for grandad . This red dress is so suitable for you ( you looked great ) , but its not appropriate to wear to a funeral. This back dress is more suitable / appropriate. Do the appropriate thing or do what is appropraite > do the thing that is correct and proper for the situation You dont hear , do the suitable thing . Whatever you find suitable/approprite will be acceptable to me.>Whatever, you find that have the qualities that suits or good for you/whatever you think is proper for the situation. Fitting > correctness and rightness of something happening> very close to appropriate in meaning . It is not fitting/appropriate of you to seat with the servants. The killer met a fitting end.