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ão is a common orthographic sequence in Portuguese, formed by the nasalized vowel a (ã) followed by o. It is not a separate letter of the alphabet, but a productive ending and syllable in many words. The combination is widely used in noun and adjective formation, as well as in some borrowed or compound terms.

Phonology and pronunciation vary by dialect, but the sequence is typically realized as a nasalized nucleus with a following labial element, commonly described as a nasal diphthong. In many Brazilian and European Portuguese varieties this is heard as a nasal vowel with a [w]-like color, often transcribed roughly as [ɐ̃w̃]. Examples include pão (bread) [pɐ̃w̃], mão (hand) [mɐ̃w̃], chão (floor) [ʃɐ̃w̃], balão (balloon) [baˈlɐ̃w̃], avião (airplane) [aˈvɐ̃w̃], and irmão (brother) [iˈmɐ̃w̃].

Morphology and usage: The ending -ão is a productive masculine noun and adjective ending in Portuguese. It appears in a wide range of common words (padrão, cidadão, casarão, avião, irmão, mão, pão, balão, chão) and can also form nouns and agents from other bases. It often conveys concrete objects, people, or abstract notions, and many -ão words carry stress on the penultimate or antepenultimate syllable, depending on each word’s history and accent marks.

Orthographic contrasts: -ão should be distinguished from ao (without tilde), which has different pronunciation in sequences like ao lado or soar in other contexts. The tilde in ã signals nasalization, a hallmark of Portuguese phonology, affecting both pronunciation and syllable structure.

See also: Portuguese orthography, nasal vowels, diacritics, Portuguese phonology.