Therefore, -   - The Greek word translated as "therefore" either emphasizes the truth of something ("certainly," "really") or it simply continues an existing narrative.

when -  The Greek word translated as "when" introduces a phrase that explains a certain condition so "whenever" or "since."

the -- The word translated as "the" is the Greek definite article. The Greek article is much closer to our demonstrative pronouns ("this," "that," "these," "those") than the English "the." See this article for more. 

owner -- The word translated as "owner " is the same word that is often translated as "Lord" or "the Lord" in the NT. It also means "lord," "master of the house," and "head of the family." It is the specific terms for the master of slaves or servants, but it was a common term of respect both for those in authority and who were honored. It was the term people used to address Christ, even though he had no formal authority. Today, we would say "boss" or "chief."

therefore

of -- This word "of"  comes from the genitive case of the following word that requires the addition of a preposition in English.  The most common is the "of" of possession.

the -- The word translated as "the" is the Greek definite article. The Greek article is much closer to our demonstrative pronouns ("this," "that," "these," "those") than the English "the." See this article for more. 

vineyard -- The Greek word for "vineyard" only means "vineyard.

cometh, -- The word translated as "cometh" primarily means "to start out" but Christ usually uses it to mean "come" but not always. It indicates movement, especially its beginning, without indicating a direction toward or away from anything, so it works either as "start," "come," or "go," but it is more like our phrase "being underway." Our English word "show up" captures both the "start" and "come" ideas. See this article for more.

what -- The word translated as "a certain" means primarily "anything" or "anyone," but can be used to mean someone of note as we would say "a someone."

will -- This helping verb "will" indicates that the verb is the future tense. Helping or auxiliary verbs are needed to translate the Greek verb forms into English.

he -- This is from the third-person, singular form of the verb.

do  - The Greek word translated as "do" has the primary meaning of "making" or producing" something or "causing" or "rendering" as service. In sentences like this, it functions more like our word "happen."

to -- This word "unto" comes from the dative case of the following word that requires the addition of a preposition in English. The most common is a "to" for the English indirect object.

those  - The word translated as "those" is an adjective that highlights its noun as being in a specific place or time from a word that means "there."

missing "the"  -- (MW) The untranslated word is the Greek definite article, which usually precedes a noun and, without a noun, takes the meaning of "the one." The Greek article is much closer to our demonstrative pronouns ("this," "that," "these," "those"). See this article for more. 

tenants?  - - (CW) The word translated as "to husbandmen" means to those "tilling the ground," and from that, "vinedresser," "gardener," and "peasant."