This kana is formed by adding dakuten (voicing marks) to the base kana 『た』 (ta), changing its pronunciation to 『だ』 (da). It is used in vocabulary and also functions as the plain form of the copula 'to be' (equivalent to 'desu' in polite form), which links subjects and predicates in sentences. For example: 『これは ほん だ』 (kore wa hon da, 'This is a book').