"Hence" basically means, "for this reason" or maybe even, "so." Her hair was as golden as the sun, hence the nickname "Sunflower." (Her hair was really yellow, so her nickname was "Sunflower") He always liked the windows open, hence the constant breeze in his room. (He prefered to have the windows open, so there was wind in his room.) The store closed at six, hence the giant "closed" sign at the door. (The store closed at six so there's a "closed" sign at the door.) Also note that in informal speaking, nobody really uses this word. It's mostly used in formal writing or something of the sort. Hope this helped! Feel free to ask me any other questions.

'Hence' in modern usage means 'therefore'. It is a formal word in English and so good to include in written documents or if you are making a formal speech or presentation. You will hear politicians use it a lot.

It's a rather archaic word, but you will encounter it now and then. It literally means "from here", and can figuratively mean "from this (idea/situation/conclusion/etc)". Bonus! We also have the archaic words "thence" and "whence". I'm sure you can guess how they work. ;)

This is difficult, because it is not a commonly used word. I have a university degree in communication, and I have never used this word. It is a word that I understand when I see it. Here's an example from linguee.com: No one can safely function alone, hence the value of gaining the wisdom of the group.