Love words? You must — there are over 200,000 words in our free online dictionary, but you are looking for one that’s only in the Merriam-Webster Unabridged Dictionary.
Start your free trial today and get unlimited access to America's largest dictionary, with:
What made you want to look up longitudinal system? Please tell us where you read or heard it (including the quote, if possible).
Can you spell these 15 tricky spelling words?
Take the quiz
Do you know these words that come from names?
Take the quiz
Test your visual vocabulary with our 10-question challenge!
Take the quiz
Listen to the words and spell through all three levels.
Play the game
