Do you know this 3 letter word in English? 

To 'the' or not to 'the'? Here are some notes on the definite article in English:
Yes, it is pronounced two different ways - this usually depends on whether the sound after it is a consonant or a vowel.
English has many many many rules on when (and when not) to use the definite article ‘the’. Some, but by no means all, are mentioned in this video. Some rules mentioned in this video include the lack of ‘the’ before talking about government institutions such as schools or prisons, and ‘the’ when used with archipelagos, mountain ranges and other geographical features.
Although some rules are different to the languages mentioned here. Spanish, for example, more frequently uses the definite article, even when talking about nouns in general. If the Beatles had been Spanish, they would have sung ‘All you need is the love, da da da da da.’ However, some rules such as when to use ‘the’ with countries, are more consistent across languages.
Sometimes one rule can be superseded by another. For example, although we don’t use ‘the’ when talking about the institution of school, we would use ‘the’ to identify a particular school (e.g. ‘I go to the school on the corner of the High Street).