When alone, the numerical term for the number 1 is "mono-" and that for 2 is "di-". In association with other numerical terms, the number 1 is represented by "hen-" (except in the case of "undeca-") and the number 2 by "do-" (except in the case of "dicta-" and "dilia-"). The numerical term for the number 11 is "undeca-". Compare monochloro with henicosane for the number 21 and dichloro with docosane for the number 22.

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