The conditional tense is used to talk about hypothetical future scenarios, it can also be used for polite requests. Anything taking place in the future using “I would” in English would qualify as the conditional in Spanish.

The conditional tense is formed by adding the endings to the infinitive for regular verbs.
For irregular verbs, it will use the same irregular stems as the simple future tense.

E.g. Me gustaría salir con mis amigos este fin de semana – I would like to go out with my friends this weekend.
Me gustaría comprar un pastel – I would like to buy a cake.

WHO ENDING
Yo (I) ía
Tu (you singular) ías
El/Ella/Usted (He/She/You polite/it) ía
Nosotros/as (We) íamos
Vosotros/as (You, informal, plural) íais
Ellos/Ellas/Ustedes (They/You, formal, plural) ían

Irregular verbs use a slightly different stem with the same endings.

Drop multiple letters from the infinitive:
Decir = dir
Hacer = har

Add ‘d’ to the infinitive:
Poner = pondr
Venir = vendr
Salir = saldr
Tener = tendr
Valer = valdr

Drop the ‘e’ from the infinitive:
Poder = podr
Querer = querr
Caber = cabr
Haber = habr
Saber = sabr

The conditional tense can also be used together with the imperfect subjunctive – there are further explanations under the “imperfect subjunctive” mini lesson.