1. The most basic form of the Spanish verb is the infinitive. Infinitives are usually seen as the equivalent of the "to" form of verbs in English, such as "to eat" and "to love." Spanish infinitives always end in -ar, -er or -ir, in that order of frequency.
2. Spanish infinitives can function as masculine nouns. For example, in "creer es la clave" (believing is the key), creer is acting like a noun.
3. Spanish verbs are extensively conjugated. Most often, the -ar, -er or -ir endings of verbs are replaced with another ending, although sometimes an ending is added to the complete verb. These endings can be used to indicate who is performing the action of the verb, when the action occurred and, to some extent, how the verb relates to other parts of the sentence.
4. Most verbs are conjugated regularly, which means that if you know the infinitive ending (such as -ar) you can predict how it will be conjugated, but the most-used verbs usually are conjugated irregularly.
5. Some verbs don't exist in all conjugated forms. These are known as defective verbs. The most common defective verbs are the weather verbs such as nevar (to snow) and llover (to rain), which are used only in the third person.
6. Spanish verbs very commonly are used without a subject. Because conjugation can indicate who is performing the action, an explicit subject often isn't necessary. For example, it is clear that "canto bien" means "I sing well," and it is not necessary to include yo, the word for "I." In other words, subject pronouns are frequently omitted.
7. Verbs can be classified as transitive or intransitive. The same is true in English. A transitive verb needs a noun or pronoun, known as an object, with it in order to express a complete thought; an intransitive verb does not. Some verbs are transitive and intransitive.
9. The subjunctive verb mood is extremely common in Spanish even though it has mostly disappeared in English.
10. When new verbs are added to the language, they are frequently given an -ear ending. Examples of such verbs, all of them imported from English, include tweetear (to tweet), surfear (to surf) and even snowboardear.