Trick or treaters are individuals who participate in the Halloween tradition: trick or treat.

In person (not hyphenated) is an adverbial phrase that describes the act of being physically present at a specific location or event. In-person (hyphenated) is an adjective that describes something occurring or involving face-to-face interaction or physical presence.

Insure is to provide financial protection against potential loss. Ensure is to make certain or guarantee that something will happen or be the case.

Tomatoes is the plural form of "tomato", which is a fruit/vegetable used in various dishes. Tomatos is the incorrect variant of the word.

Independent variable is the variable that researchers change in an experiment to observe its effect on another variable. Dependent variable is affected as a result of changes in the independent variable.

Both words refer to a person's skills and abilities; the difference in use pertains to many factors.

Among and amongst both refer to being in the midst of a group . However, "among" is more common in American English, while "amongst" is more commonly used in British English.

Per se is used to emphasize that something is considered in and of itself, while per say is the incorrect usage of this term.

Sometime is an adverb that refers to an unspecified point in time in the future or past. Some time, as a phrase, typically refers to a period of time that is not precisely defined.