The Spanish words you already know

English and Spanish did not borrow from each other much; they both borrowed heavily from Latin. English took its Latin vocabulary through French and later directly from scholarly Latin, while Spanish descends from spoken Latin outright. The result is a very large shared layer that neither language passed to the other.

That common ancestry is why the correspondences are so regular. -tion and -ción are not a coincidence of two words; they are the same Latin ending arriving twice, which is why the pattern holds across hundreds of items rather than a handful.

More recently the traffic has reversed, and Spanish has taken a set of modern words straight from English - el fútbol, el internet, un clic. These are easy in the other direction and are marked as borrowings in the data rather than as inherited relatives.

Spanish has some of the most notorious false friends of any language paired with English, and they are common words rather than obscure ones. Embarazada does not mean embarrassed. Éxito is a success, not an exit. Ropa is clothing, not rope. These are frequent enough to matter in the first weeks.

Gender does not come with the shared spelling. Knowing that información exists tells you nothing about whether it is el or la, and the ending rules that predict gender are a separate thing to learn - although -ción is reliably feminine, which is a useful pairing with the rule above.

A shared root does not guarantee a shared register. Some Spanish words that look like formal English are entirely ordinary in Spanish, and using the English one at the same level will sound stiff.

Learn -ción and -idad first. Between them they cover an enormous amount of abstract vocabulary, and both map to English endings you already use without thinking.

Add -oso for -ous and -mente for -ly next; the first gives you adjectives and the second gives you adverbs, so a small amount of memorisation buys you two whole word classes.

Read the false friends deliberately rather than hoping to absorb them. The Spanish set is short, high-frequency and genuinely embarrassing to get wrong.