The word cognates derives from Latin cognatus, “blood relative”
Characteristics of cognates
Cognates need not have the same meaning: dish (English) and tisch (“table”Genrman) and desco (table, medieval Italian), or starve (English) and sterben (“die”, German),or head (English) and xhef (“chief, head”, French), serve as examples as to how cognate term may diverge in meaning as languages develop separately, eventually becoming false friends.
Cognates across languages
Examples in Indo-European languages are the words night (English), nuit (French), Nacht (German), nacht (Dutch), nicht (Scots) natt (Swedish, Norwegian), nat (Danish), raat (Urdu), nátt (Faroese), nótt (Icelandic), noc (Czech, Slovak, Polish), ночь, noch (Russian), ноќ, noć (Macedonian), нощ, nosht (Bulgarian), ніч , nich (Ukrainian), ноч , noch / noč (Belarusian), noć (Croatian), ноћ/noć (Serbian), νύξ, nyx (Ancient Greek, νύχτα / nyhta in Modern Greek), nox (Latin), etc.
noche (Spanish), nos (Welsh), noite (Portuguese and Galician), notte (Italian), nit (Catalan), noapte (Romanian), nakts (Latvian) and naktis (Lithuanian), all meaning "night" and derived from the Proto-Indo-European (PIE) *nókʷts , "night".
Cognates may often be less easily recognised
The English word milk is clearly a cognate of German Milch, Russian молоко (moloko)
and Croatian mlijeko. On the other hand, French lait and Spanish leche (both meaning "milk") are less obviously cognates of Ancient Greek γάλακτος (genitive singular of γάλα, "milk") , a relationship more evidently seen through the intermediate Latin lac "milk", as well as the English word lactic and other terms borrowed from Latin
There are literally tousands of words that are the same or similar in appearence in English and Spanish, and have the same meaning in both languages “cognates”. There are also, however, many instances where appearances are deceiving and words that look alike are quite different in meaning “false cognates”.
Are words that are commonly thought to be related (have a common origin) whereas linguistic examination reveals they are unrelated
FALSE COGNATES Sometimes a word in Spanish will sound like or seem like a similar one in English. In the Spanish language there are a number of false cognates like this. So you have to be careful or you might make a mistake and say, "Estoy embarazada," to mean that you are embarrassed, when actually you will be saying that you're pregnant!
Is “actual” a cognate?
In Spanish, means “present, current”, and not “actual” as we use it in English, which in Spanish is instead real, verdadero.