Here is a context clues worksheet on the noun circumstance. This word is used mostly in the plural, and I’ve written the context clues to reflect that. Nonetheless, Merriam-Webster’s Collegiate Dictionary, 11th Edition (the dictionary of record at Mark’s Text Terminal), lists it in the singular, which is how I too list it.
If you find typos in this document, I would appreciate a notification. And, as always, if you find this material useful in your practice, I would be grateful to hear what you think of it. I seek your peer review.