Franklin did not, of course, invent electricity, but he discovered many things about it, previously not understood.
Before Franklin started his scientific experimentation, it was thought that electricity consisted of two opposing forces. Franklin showed that electricity consisted of a "common element" which he named "electric fire." Further, electricity was "fluid" like a liquid. It passed from one body to another — however it was never destroyed. In a letter to Peter Collinson, Franklin wrote that the
"fire only circulates. Hence have arisen some new items among us. We say B (and other Bodies alike circumstanced) are electricised positively; A negatively; Or rather B is electricised plus and A minus ... These terms we may use till philosophers give us better."
Franklin's work became the basis for the single fluid theory. When something is being charged, such as a car battery, electricity flows from a positive body, that with an excess charge, to a negative body, that with negative charge. Indeed, a car battery has plus and minus signs on its terminals.
Franklin wrote Collinson in another letter that: "I feel a Want of Terms here and doubt much whether I shall be able to make this intelligible." Not only did Franklin have to posit theories, he also had to create a new language to fit them. Some of the electrical terms which Franklin coined during his experiments include:
They are still the terms we use today.