Sun versus sun..... ?

*grammar does not have an e in it.

Raymond's answer is the most accurate and most complete.

The proper name for the Sun, in English, is, the Sun, notice the "the" and the capitalization. In scientific journals other stars are never refered to as suns. The term 'Sol' is a proper name in Latin, and commonly used in science fiction, never by English written scientific authors.

The same is said of the Moon, (not Luna, once again, Latin and science fiction), however, I do often see 'moons' instead of 'satellites' when referring to objects in orbit around other plants, even on the NASA/JPL website, so that term is evolving to cover any satellite around a planet.

With a small s, it is used as a "simile", to mean "something like our Sun".

In astronomy, the official word for these other "suns" is "star".

Same thing about these objects that are "like our Moon", for example, the "moons of Jupiter" are really called "satellites" in official papers.

Sol is the Latin name of our Sun (from the Roman mythology, after it mirrored the Greek mythology, where the Sun was Helios). Sol is NOT an official name of the Sun in English.

However, there are real scientific terms that are constructed from the Latin and Greek names, such as solar and heliocentric.

In literature (other than scientific), it is quite acceptable to talk of suns and moons; many classical authors have done so.

Like many words, "Sun" has several definitions.

It is indeed used as another word for a star, usually a star with planets in its system. A great many science fiction stories use the word to mean a star. It is also used as a general term for a star by narrators of science documentaries on TV.

In English, "Sun" when used as the name of our star is capitalized.

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Only if the garbage is the company's brand name. Then it will begin with a capital letter.

What regards to our Sun, yes, you have to have the "S" as a capital letter. The same is for our Moon.

I have never heard of that. I believe that its garbage and should be thrown away. When writing about our sun, you don't have to put the "s" in sun as a capital letter but the "s" in Sol needs to be capitalized because its a name.

I would think of it as this.... We live on the planet Earth, but we do not have Earthquakes or use Earth-movers in construction. These words on get "capital" treatment when used at the first word of a sentence.

In general, a "sun" can be any star with planets. When it's capitalized, it's a reference to 'our' sun. Er... Sun.