být

1. Word Order (Clitics):
The forms jsem, jsi, jsme, jste are usually unstressed words called second-position clitics. They naturally want to sit in the second position of a sentence, right after the first stressed word or phrase (e.g., Dnes jsme unavení. = Today we are tired.). However, when acting as the main verb with a dropped subject pronoun, they can start a sentence (e.g., Jsem doma. = I am at home.). When they do this, they take on word stress and act as regular words rather than clitics. This is an important contrast to when they are used as helper verbs in the past tense. As helper verbs, they are strict clitics and absolutely cannot start a sentence (e.g., Byl jsem doma. is correct, but Jsem byl doma. is ungrammatical).

2. Negation:
To make the verb negative, add the prefix ne- (nejsem, nejsi, nejsme, nejste, nejsou). However, the 3rd person singular is highly irregular: it is není (never "neje").

3. "There is / There are":
Unlike English, Czech doesn't use a dummy word like "there" to say something exists. You simply use je or jsou, often paired with a location word like tady or tu (here) to sound natural (e.g., Je tu problém. = There is a problem).

4. Using Pronouns:
While pronouns are usually dropped, you should use them when you need to establish contrast or emphasis (e.g., Já jsem Čech, ale on je Slovák. = I am Czech, but he is Slovak.).

5. Stating Professions:
When stating your profession, you can simply use být with the noun in its basic form (e.g., Jsem učitel. = I am a teacher.). This is perfectly fine for beginners and very common in everyday speech. In more formal written Czech, you might also see the Instrumental case used for professions (e.g., Jsem učitelem.).

6. Gender Agreement:
Remember that adjectives and nouns following the verb být must agree with the subject's gender. While the examples above use masculine forms, a female speaker would use feminine forms: Jsem unavená (I am tired), Jsem Češka (I am Czech), and Jsem učitelka (I am a teacher).