Hundred

One hundred (100) is a natural number. In scientific notation, it is written as 10². The standard SI prefix for a hundred is "hecto-". The Roman numeral for hundred is C (for centum).

Other uses include:

• Hundred Days
• Hundred Years' War
• Hundred Schools of Thought
• Hundred Flowers Campaign
• Hundred Days' Reform
• Battle of Hundred Regiments

See also: Hundred (division), century, the year AD 100

One hundred and one / One-O-One

101 is also used as a suffix for "basic course in...", like: 'How to build violins 101'. It originates from having the name of a first-stage class suffixed with 101, eg. "Calculus 101" as opposed to "Calculus 203", and so on.

Note this usage is not global.

See also: the year AD 101