Definite article

Question

Is there a rule for using the definite article in Spanish? It often trips me up. It doesn’t always follow the same pattern as English, eg in Castles text: …visitar castillos (no ‘los’, where in English there would be no ‘the’), but then:… la historia de los castillos medievales (in the  English version there is no ‘the’, the history of medieval castles; the history of the medieval castles is not incorrect it just has a different meaning).  Maybe, as in English, it’s very much about common usage and there’s no absolute rule.?

Answer

Hola Matthew
The presence vs omission of the article is one of the most difficult things to master in Spanish. As you suspected there is no specific rule. There is a general rule that establishes that the presence of the article is often linked to being more specific about something while the omission gives more of a general meaning. For example, in "I usually visit castles" we are naturally dropping the article because they are referring to castles in general, however in "the history of the medieval castles" we include it as this time we are being more specific, we are talking about this type of castles: "los castillos medievales". 
We have a lesson where the presence or omission of the article is clearer. Have a look here.
And if you type "definite article" in the search (top right corner) some other lessons related to the definite article will show up. 
Alternatively, you can see lessons on this topic here under "artículo definido".
I hope it helps.
Saludos cordiales
Inma

Answer

I have a theory that several centuries of contact with Arabic - is the reason why Spanish often puts in the definite article when English does not. [This practice is extremely common in written and spoken Arabic, and indeed in the English spoken in India and Pakistan, perhaps influenced in the same way?]

Answer

Hola David

That sounds interesting. I've never heard that sort of grammatical influence from the Arabic but it could be? (I don't speak the language though so don't know how they use the articles)

You always hear and read about their influence in vocabulary, but not so much about grammatical aspects like this.

Saludos