In simple words, e, i, c, r, are the only letters that can be written double. In compound words, all the vowels, and also n and s, are written double whenever any of them are the last of the component, and the first of the word to be compounded.
The following words and phrases will be found useful:
VERBS.
Infinitive.
To have. To be.
Haber.Tener.[1] Ser. Estar.
gerund
Having.Being.
Habiendo.Teniendo. Siendo. Estando.
PAST PARTICIPLE.
Had.Been.
Habido.Tenido. Sido. Estado.
Indicative Mood.
PRESENT TENSE.
I Have.I am.
1. He. |
Tengo. |
Soy. |
Estoy. |
IMPERFECT TENSE.
I Had.I was.
1. Habia. |
Tenia. |
Era. |
Estaba. |
- ↑ Tener means "to have" in the possessive sense.