WOW, really amazing equations!

2 types of clauses based on its role: - dependent clause - independent clause

4 types of sentences based on its structure: - simple sentence - complex sentence - compound sentence - compound-complex sentence

4 types of sentences based on its functions: - declarative sentence - imperative sentence - exclamatory sentence - interrogative sentence

A sentence can be a single clause or several clauses. A sentence which contains only one independent clause is known as a simple sentence. A sentence which contains one independent clause and at least one dependent clause is known as a complex sentence. A sentence which contains two or more independent clauses is known as a compound sentence. A sentence which contains at least two independent clauses and at least one dependent clause is known as a compound-complex sentence.

优先学习德语或法语，然后再学习英语。 德语在发音语法方面都很严谨规整，构词多以合成词为主，极少有例外（这很德国）。 英语在各方面都比较灵活多变，包含大量的特殊情况，不规则用法等。 所以德语入门比较难，但之后会轻松不少，英语入门很容易，但想要进阶是需要长时间的积累。 Language English is a child of Germany and French, really? LOL

Spaced Repetition: * the rate of decay * the timing of active recall * the sweet spot of forgetting