In Spanish grammar, adjectives must agree with the nouns they modify in terms of gender and number. This means that the adjective endings will change depending on whether the noun is masculine, feminine, singular, or plural. The most common endings for adjectives are “-o” for masculine singular, “-a” for feminine singular, “-os” for masculine plural, and “-as” for feminine plural. Practicing adjective ending exercises can help you become more familiar with these rules and improve your overall Spanish language skills.