In a primary (1°) halogenoalkane, the carbon which carries the halogen atom is only attached to one other alkyl group.
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For $\ce{CH3Cl}$, the carbon which carries the halogen atom has no other alkyl groups attached, yet my class notes say "the alkyl halide has a primary centre". So is a primary alkyl group one with is attached to 0 or 1 other alkyl group and not just 1?