Art. 1. Any single thing, as a peach, a rose, a book, &c., is called a unit, or one ; if another single thing is put with it, the collection is called two; if another still, it is called three ; if another, four; if another, five, &c.

The terms, one, two, three, four, five, &c., by which we designate how many single things or units are under consideration, are the names or expressions of numbers. Hence,

2. Number signifies a unit, or a collection of units.

OBs. Numbers have various properties and relations, and are applied to various computations and practical concerns of life. These properties and applications are formed into a system, called Arithmetic. Hence,

3. ARITHMETIC is the science of numbers.

Numbers are usually denoted by certain letters of the alphabet ; or by arbitrary characters called figures.

QUEST.-1. What is a single thing called ? If another is put with it, what is the collection called? If another, what? What are the terms one, two, three, &c. ? 2. What does number signify? Obs. To what are numbers applied ? 3. What is Arithmetic ? How are numbers usually denoted ?