How to spell STIMULS correctly?

If you meant "stimulus", that's the correct spelling. Alternatively, it could be "stimulate" or "stimulation". Double-check your context to ensure the proper term is being used.

• stills The photographer captured stunning stills of the landscape at dawn.
• Stimuli The researcher presented various stimuli to measure the participants' reaction time.
• stimulus The government provided a stimulus to boost the economy.

Excatally

• exact
• exacted
• exactingly
• exactly
• exacts
• executable
• exotically
• extol
• inexactly
• oxtail