In phonology, the most prominent distinguishing element of Peninsular Spanish varieties, except for the southernmost ones, is the preservation of a distinction between the phonemes /s/ and /θ/, represented respectively with the letters ⟨s⟩ on one hand and ⟨z⟩, or ⟨c⟩ before ⟨e / i⟩, on the other. This is usually called distinción in Spanish, while the merger of both phonemes is called seseo. While in the Spanish of the Americas and in parts of southern Spain ⟨z⟩, ⟨c⟩ before ⟨e / i⟩, and ⟨s⟩, are typically read roughly like the English /s/, in the Peninsular dialects with distinción, ⟨z⟩, and ⟨c⟩ before ⟨e / i⟩, are read aloud as [θ], that is, the initial sound of the English word think. However, many Andalusian dialects and the Spanish spoken in the Canary Islands do not use distinción as a general rule, but rather use either seseo or ceceo.
In morphology, the most notable distinguishing feature of Peninsular Spanish is the use of the pronoun vosotros (along with its oblique form os) and its corresponding verb forms for the second person plural familiar. In virtually all other varieties of Modern Spanish, for the second person plural, the familiar and the formal are merged in ustedes, with its verb forms. Again, the use of vosotros is uncommon in the Canary Islands and only partially introduced in Western Andalusia.