Blessed -- (CW) The word "blessed" in Greek is an adjective from a root word meaning "happy" or "fortunate." In Jesus's era, all luck was attributed to divine favor but this is not otherwise a religious word. It has no relationship to the Greek verb "bless" or the noun "blessings." This word can also mean "wealthy". This sets up an interesting play on words that only works in Greek, saying "wealthy the poor,"

are -- There is no verb "are" in the Greek source. It is implied by the equating of "workman" with "worthy" both in the Greek form of subjects.

the -- The word translated as "the" 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. 

poor -- (CW)  The Greek word translated as "poor" means "a beggar." It is the subject of the phrase and plural, "beggars." The first two words are literally, "Lucky these beggars."

in  -- (CW) This word "in" comes from the dative case of the following word that requires the addition of a preposition in English, but the translator must decide which preposition to use: a "to" as an indirect object, a "with" for instruments, an "in" for locations, an "as" for purposes, an "of" for possession, a "by" for agents, an "as" for comparisons, "at" or "on" a time, and an "in" for area of effect. Though it can mean "of," Jesus and all other koine speakers would usually use the genitive form to indicate a possessive. Though it can be "in," Jesus usually uses a possessive.

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. 

spirit: -- The word translated as "spirit" primarily means "breath", "wind," a "non-material being", and "blast." Like "spirit" in English, it can also mean "attitude" or "motivation.' It also means the "breath of life," from which we get to "spirit" and "spiritual." Its meaning as "the breath of life" is brought out by the idea of creating life. Its meaning as "spiritual" is brought out by the contrast with "physical". Read more about this word in this article on the holy spirit. 

for -- The "for" here is a causal adverb that means "seeing that", "because", or "since."

theirs -- (CW) This is the genitive, plural pronoun. When this form or word is the object of the verb "to be" the sense is "belongs to," so the sense of this word in these situations is "to." This is not the specific meaning of the word in this situation , which is "to them."

is  -- (CW) The verb "is" here is the common form of "to be" in Greek. It means to have a certain characteristic or remain in a certain condition. It also equates terms or assigns characteristics.  With an object in the possessive form the "is" becomes "is of," which can mean "it is descended from," "it is the type of," "it belongs to," "is made of," "is a duty of," "is at the mercy of," or " is dependent on."  

the -- The word translated as "the" 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. 

kingdom -- 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.

of -- This word "of"  comes from the genitive case of the following word that required the addition of a preposition in English.  The most common is the "of" of possession, but it can also mean "belonging to," "part of", "which is", "than" (in comparisons), or  "for", "concerning" or "about" with transitive nouns. 

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. 

heaven. -- (WN) The word translated as "heaven" means sky, the climate, and the universe. It also meant the home of the gods in a physical sense: the sun, moon, and planets were named for the gods.  The word is plural, not singular.