Some Latin loanwords do not change in the plural:
el déficit‘deficit’ los déficit‘deficits’3.1.2 In all the above cases, the stress pattern of the singular is kept in the plural (and so
adjustments in spelling sometimes have to be made, e.g. el origen‘origin’/los orígenes
‘origins’. However, there are three words in which the stress is changed in the plural:
el carácter‘character’ los caracteres‘characters’
el régimen‘régime’; ‘diet’ los regímenes‘régimes’, ‘diets’
el espécimen‘specimen’ los especímenes‘specimens’
3.1.3 Compound nouns which are written as one word follow the rules given in 3.1.1:
el altavoz‘loudspeaker’ los altavoces‘loudspeakers’
el sacacorchos‘corkscrew’ los sacacorchos‘corkscrews’3.1.4 Many nouns used adjectivally (see 2.6 Class 4) are invariable in the plural.3.1.5 When surnames are used in the plural to indicate a family, they are usually left in the
singular form:
los Moreno‘the Morenos’
los Pérez‘the Pérez family’3.2 Number agreement
3.2.1 Adjectives agree in number (i.e. they are singular or plural) with the noun or noun
phrase to which they relate:
unas cuestiones (pl.) candentes (pl.)
some burning questionsdistintas (pl.) interpretaciones (pl.) de las cifras
various interpretations of the figures
A combination of two singular nouns in a noun phrase is equivalent to a plural:
el lápiz (sg.) y el bolígrafo (sg.) rojos (pl.)
the red pencil and biro
If the adjective precedes a combination of singular nouns, however, it is usually left in
the singular to avoid an odd-sounding sequence:
con enorme (sg.) cuidado (sg.) y precisión (sg.)
with enormous care and precision3.2.2 Agreement between subject and verb3.2.2.1 The verb agrees in number with its subject, whatever its position:
El tren llega a las ocho. The train arrives at eight.
Cantan los pájaros. The birds are singing.3.2.2.2 There is some variation with subjects which function as collective nouns, such as la
mayoría‘the majority’, la mitad‘half’, el resto‘the rest’, etc. Strictly speaking, since
Number agreement 3.2