A disc or disk is a flat, typically circular object or surface with a defined edge. The difference in spelling depends on whether the object is used in the context of American or British English, and also its usage.

Okay is derived from OK, and both are able to be used interchangeably in any context. Both are often used to indicate agreement, approval, acceptance, or affirmation of something.

"Masters" should not be used interchangeably with "master's". "Master's" with an apostrophe is primarily used to denote possession or association with an advanced degree.

"Lenses" encompass multiple optical components or a collection of different lenses while "lens" refers to a single optical element.

Sargent is a surname or given name, while sergeant is a military rank denoting a non-commissioned officer responsible for leadership and supervision in the armed forces.

"Fare" denotes the price you pay for a ticket or the food you enjoy at the event while "fair" refers to an event with rides and games. "Fair" also means just, equitable, or free from bias or favoritism, pleasing in appearance and good weather conditions.

"Realise" is the British English spelling, while "realize" is the American English spelling. Both are verbs that mean to become aware of something.

For formal writing, academic papers, and professional communication, it is advisable to avoid "irregardless", as the word can be viewed as incorrect, and opt for the accepted term "regardless" to ensure clarity and correctness in your language use.

The difference between Eastern Standard Time (EST) and Eastern Daylight Time (EDT) lies primarily in their observance of daylight saving time (DST).