girl
The German word for 'girl' is 'Mädchen'. It is a common noun and is used to refer to a young female. It is often used in everyday conversation and writing. It is important to note that unlike in English, German nouns are always capitalized.
The girl is reading a book.
This sentence uses 'Mädchen' to refer to a girl who is in the process of reading a book. In German, the present continuous tense is often expressed in the same way as the simple present tense, hence 'liest' can mean 'is reading' or 'reads'.
The girl is my sister.
In this example, 'Mädchen' is used to denote the speaker's sister. The verb 'ist' (is) is used to equate the 'girl' (Mädchen) with the speaker's sister. Sentence structure in German typically follows the subject-verb-object format, similar to English.
The girl is playing piano.
This use of 'Mädchen' identifies a girl who is playing the piano. As in the first example, the present continuous tense can be expressed as the simple present tense, so 'spielt' translates as 'is playing' or 'plays'. Note the order of subject, verb, and object is the same as in English.