L'usage des prépositions.
Salut mes amis!
J'étais en train d'écouter une vieille chanson "The world I know" (Le monde que je connais).
Comment puis-je savoir quand l'usage de la préposition est correcte ou non?
Pourquoi n'est pas "The world that I know"?
I'm not super knowledgeable of English grammar, however, English is my native language and I'm pretty sure that the grammatically correct way to say it would be "the world that I know" as you have said. Saying "the world I know" would be incorrect but it would be what you would most likely hear an English speaker say if he/she were casually talking to someone, but in a more formal instance it would be said the way (that) you correctly pointed out. I put a parentheses around the final "that" in my sentence because it too would be left out in a casual conversation. It's difficult to explain when you should or shouldn't add the preposition because there are so many individual cases and there's not really a rule. It's more based off of whether the construction sounds correct since technically it should always be included. I would recommend to just learn the correct way and always add it and if you get to a level where you're communicating with English speakers regularly you will naturally learn casual English, and god help you because a lot of it makes no sense xD
I've been thinking about your question a little more and I realized that when you have a sentence construction like: noun + that I + verb, "that" is optional. This has worked for all of the sentences I made up. Some sound better than others but this generally works just fine. When you have noun + that + verb or noun + that is + adjective on the other hand, you need to include "that"
1) the house that I own > same as but more formal than "the house I own"
2) the wind that blows > similar but not the same as "the wind blows"
3) the car that is blue > similar but not the same as "the car is blue"
En anglais, le mot "that" peut être traduit par "qui/que" (que quand il s'agit d'un sujet après et qui quand il s'agit d'un verbe après). En anglais, "que" est optionnel et du coup est à votre choix. Cependant, le mot "qui" est obligatoire et doit être utilisé. Bien sûr qu'il y a quelques petites exceptions (je pense), mais il n'y en a pas beaucoup.
La personne que j'aime = The person (that) I like. Optionnel
La personne qui m'aime = The person that likes me. Non-optionnel