What is the meaning of -a-?

Connective infix encountered in loanwords and phrases, generally no longer carrying a distinct meaning.

Replacing carbon, especially in a ring.

Forms the past perfect tense in verbs.

gnomic aspect marker, indefinite present marker

present tense marker used in headlines

Forms the recent past tense.

Forms the past tense. It goes between the class/person concord and the past tense endings.

Source: wiktionary.org

See also