πλὴν [20 verses](prep/adv)  "But" is from plen, which is a preposition meaning "except," or "save," with the genitive object, as a conjunction, "besides," and "in addition to." Often used with the negative as a conjunction, "except not." Used to change the subject, "except," "however," and "but." -- The word translated as "nevertheless" is a less common preposition used like a conjunction that means "except," "save," with an object in the possessive form, or "besides," and "in addition to." Often used with the negative as a conjunction, "except not." Used to change the subject, "except," "however," and "but."

ζητεῖτε, [36 verses](verb 2nd pl pres imperat act) "Seek" is zeteo, which means "inquire for," "search for," "seek after," "desire," and "feel the want of." -- The Greek verb translated as "seek" has a variety of meanings around the idea of "searching" and "desiring." It has a sense of seeking with a specific aim. It also means to "search," "inquire into," "investigate," and "examine."

τὴν [821 verses](article sg masc acc)  "The" is the Greek definite article, hos, ("the").   It usually precedes a noun or changes the word it precedes (adjective, infinitive, participle, etc.) to act like a noun. When not preceding a a word that can become a noun, takes the meaning of "the one" or, in the plural, "the ones."  -- The word translated as "the" is the Greek definite article, "the," which usually precedes a noun or changes the word it precedes (adjective, infinitive, participle, etc.) to act like a noun. The Greek article is much closer to our demonstrative pronouns ("this," "that," "these," "those") than the English "the." See this article for more. 

βασιλείαν  [98 verses](adj sg fem acc) "Kingdom" is basileia, which means "kingdom," "dominion," "hereditary monarchy," "kingly office," (passive) "being ruled by a king," and "reign." -- The word translated as "kingdom" can be the region, the reign, the castle or the authority of a ruler. Christ does not seem to use it to mean a physical region, so its translation as "reign" or "realm" seems more appropriate. This is especially true because the "reign" of a king means the execution of his will.

καὶ [1089 verses](conj/adv) "And" is kai, which is the conjunction joining phrases and clauses, "and," or "also." After words implying sameness, "as" (the same opinion as you). Used in series, joins positive with negative "Not only...but also." Also used to give emphasis, "even," "also," and "just." In a series, it can be translated as "not only...but also." After words implying sameness "as." -- The Greek word translated as "and" is used as the conjunction "and," but it also is used to add emphasis, "even," "also," and "just."

ταῦτα [96 verses](adj pl neut acc) "These things" is tauta, which is a referring pronoun meaning "these," "this," "that," and "here." It can mean the nearer or the further depending on usage. When ταῦτα and ἐκεῖνος refer to two things ἐκεῖνος, which normally means "the nearer" as well belongs to the more remote, "the latter" in time, place, or thought, οὗτος to "the nearer".- The "these" is a pronoun that can mean "this" or "that," "here," or "there" the nearer or the further depending on usage. When the noun already has an article, it meaning is "here." It is often used in the neuter plural without a noun to refer to "these things." things -- This "things"  is from the plural, neuter form of the previous adjective.

προστεθήσεται [7 verses] (3rd sg fut ind pass) "Shall be added" is prostithemi, which is formed from two root words that mean "to put towards" and means to "put to", "to hold close", "to apply medicine [to a wound]", "to hand over", "to give something more", "to impose upon", "to attribute to", "to add", "to agree", "to associate with", "to bring upon oneself," and "to apply to oneself." -- The Greek word translated as "shall be added" means "to apply", "to deliver," "to impose upon," and many other meanings. It has the general sense of "increase."

ὑμῖν [289 verses](pron 2nd pl dat) "To you" is humin the plural form of the pronoun of the second person, "you." As the object of a preposition, this form implies no movement, but in a fixed position or events occur at a specified time or while the action was being performed. With the "to be," it acts as a possessive, "yours." to -- This word "to" comes from the indirect object form of the following word that requires the addition of a preposition in English. The most common is a "to" for the English indirect object. -- The Greek pronoun "you" here is plural and in the form of an indirect object, "to you," "for you," etc.