It has been used as the symbol... is correct here. Use Present Perfect when the action referred to started in the past, and either continues (or continues to have relevance) at the time of speaking.

Jun 13, 2019 · What is the negative form of "I used to be"? I often hear "I didn't used to be" but that sounds awfully wrong in my ears.

Apr 18, 2017 · Here is a question that has been nagging me for a few years: Which is the right usage: "Didn't used to" or "didn't use to?" Examples: We lived on the coast for years but we didn't use to go …

Oct 27, 2015 · I am trying to find out if this question is correct. Did Wang Bo used to be awkward? Should I write "use to be" instead of "used to be," or is "used to be" correct in this sentence?

Apr 12, 2011 · Bryan Garner, Garner's Modern American Usage, fourth edition (2016) provides what I take to be the current (and traditional) formal prescriptivist view among U.S. usage authorities of …

Jan 7, 2012 · 0 Mr. is most typically used with either the man's last name alone, or last name and selected other parts of the name. But that is for polite society. In everyday use, it is often appended …

Nov 8, 2010 · The animals were frequently used as a model organism in the 19th and 20th centuries, resulting in the epithet "guinea pig" for a test subject, but have since been largely replaced by other …

Oct 21, 2010 · I have used cocaine. I took cocaine at least once sometime in the past. I was using cocaine. In the past, I was a habitual user of cocaine. EDIT: As the comment says, this can also …

Jul 28, 2017 · The AMA Manual of Style says: Thin spaces should be used before and after the following mathematical symbols: ±, =, <, >, ≤, ≥, +, −, ÷, ×, ·, ≈, ∼, ∩, ∫, Π, Σ, and |. a ± b a = b a + b a − b a ÷ b …

While an apostrophe is used to indicate possession and contractions, it is not generally necessary to use an apostrophe simply to show the plural form of most acronyms, initialisms, or abbreviations, except …