The Spanish word 'no' comes directly from the Latin word 'non', meaning 'not' or 'no'. This is one of the most fundamental and unchanged words from Latin to Spanish, with just the final 'n' being dropped in the evolution from Latin to modern Spanish. The meaning has remained essentially identical over the centuries, serving as the basic negative particle in both languages.

The word 'no' is itself one of the most basic Spanish words, but it appears as a prefix in many Spanish words like 'ningún' (none), 'nunca' (never), and 'ni' (nor, neither), all sharing the concept of negation.

English speakers will find many familiar words that share the same Latin root 'non-', such as 'non-' as a prefix (as in 'nonexistent', 'nonprofit'), 'none', and 'negative'. The word 'no' itself in English comes from the same Proto-Germanic root, but is ultimately related to the same ancient Indo-European source as Latin 'non'.