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Nona- is a combining form used like a prefix meaning “nine” or “ninth.” It is used in a number of scientific and other technical terms.

In chemistry, nona– is specifically used to indicate nine atoms or nine groups of atoms in compounds, e.g., .

Nona- comes from the Latin ��ō�Գܲ�, meaning “ninth.” The word noon also derives from the Latin ��ō�Բ� ��ō����, the “ninth hour” from sunrise. That means 12 o’clock noon was originally 3 p.m!

The Greek word for “nine” is ��Բ�é��, source of the combining form ennea-, which you can learn more about in our �y��vlogs That Use article for the form.

What are variants of nona-?

When combined with words or word elements that begin with a vowel, nona- becomes non-, as in nonyl alcohol.

However, in a great many more instances, the letters non- at the beginning of a word are the prefix non-, meaning “not,” as in nonabrasive or nonacademic.

A nonagon is a polygon having nine angles and nine sides. A nonagon is also known as an enneagon.

The first part of the word, nona-, means “nine.” The -gon portion of the word may also look familiar: it is a combining form meaning “angled” or “angular,” from the Greek ��ō��í��. Nonagon literally translates to “nine-angled.”

What are some words that use the combining form nona- or non-?

• nonagenarian (using the equivalent form of nona- in Latin)
• nonary (using the equivalent form of nona- in Latin)
• nonillion (using the equivalent form of non- in French)

What are some other forms that nona- may be commonly confused with?

• nano-
• nomo-
• non- (in the sense of “not”)
• normo-

A septuagenarian is a person in their 70s (between 70–80 years old). An octogenarian is in their 80s. A nonagenarian, then, is in their ___?