In Slovene, the use of the dual is mandatory except for nouns that are natural pairs, such as trousers, eyes, ears, lips, hands, arms, legs, feet, kidneys, breasts, lungs, etc., for which the plural form has to be used unless one wants to stress that something is true for both one and the other part. For example, one says "oči me bolijo" (my eyes hurt), but if they want to stress that both their eyes hurt, they say "obe očesi me bolita". When using the pronoun "obe/oba" (both), the dual form that follows is mandatory.