This is the 2016th most frequent Russian word.
форме
"Forme" is the dative or prepositional case of "форма," meaning "shape," "form," or "manner."
In this sentence, 'форме' refers to the format or structure of the written text, specifying that it is stylistically designed as a letter.
Этот текст написан в форме письма.
This text is written in the form of a letter.
Here, 'форме' is used to describe physical condition or well-being, suggesting fitness and health.
Чтобы быть в хорошей форме, надо регулярно заниматься спортом.
To be in good shape, it's necessary to exercise regularly.
In this context, 'форме' signifies the medium or mode in which the form should be completed, specifically electronically.