This is the 8661st most frequent Russian word.
п
The letter "п" is the 17th letter of the Russian alphabet, representing the "p" sound in English.
The 'п' is part of the past tense verb 'написал', showing the verb's stem and action of writing.
Он написал письмо.
He wrote a letter.
The 'п' starts the proper noun 'Петя', which is a personal name, and also starts 'парке', referring to its role in the locational noun.
Петя увидел друга в парке.
Pety saw a friend in the park.
The 'п' appears in 'записаться', part of the verb, contributing to its meaning of signing up.