Not to be confused with Hera, the Greek Goddess.
Herra [ˈherrɑ] means "Lord" in Finnish, and is now generally used in Finnish as an honorific for all men, the equivalent to the English titles "Mister" and "Sir" and also to "gentleman". In the Finnish Defence Forces, a superior is addressed with herra followed by the rank of the superior. The address starts the conversation, but is not repeated. For example, herra luutnantti is the same address as "Lieutenant Sir!"
Written herra Halonen or hra Halonen, the plural is herrat. This title is commonly not prefixed to a first name, as it connotates a lord in past centuries (e.g. herra Kaarle or Kaarle-herra gives an impression similar to that of Mylord Charles or Lord Charles). This formal form of address is rare, used in the army and in the parliament.
In earlier centuries of the civilization, herra, similar to Lord, Sieur, Seigneur, and Freiherr, meant the owner of a lordship. The Finnish noble rank vapaaherra (baron) is quite much a continuation of this meaning. Usually, noble landowners and high priests were "herra". At those times, no commoner would have been called as herra. Indeed, several older fiction works show that commoners would react to being called herra with derision ("I am no herra!").
When capitalized, "Herra" refers to The Lord, i.e. Christian God.
Rouva is the usual female counterpart of herra. Its meaning has evolved in quite similar manner, to the honorific today signifying a married woman. In the Finnish Defence Forces, this corresponds to herra, e.g. rouva luutnantti. The equivalent of Miss is neiti.
Whereas the more archaic female variant, herratar has not so evolved - its meaning and impression given by its use, is still that of the feudal fiefholder.