This is the 3911th most frequent Russian word.
вторая
"Second" (feminine form).
The word 'вторая' is used here as an ordinal numeral to indicate the position of the book.
Это вторая книга на полке.
This is the second book on the shelf.
The word 'вторая' is used here to describe a specific segment of the day, functioning as an adjective.
На вторая половина дня запланирован отпуск.
The vacation is planned for the second half of the day.
The word 'вторая' is used here as an ordinal numeral to describe the position in the queue.