Then  - -- The "then"  is from an adverb meaning "when," "at what time," "at some time or other," "at some unknown time, and "at some time in the future." With the subjective negative ) before it, the sense is "not when."

saith  - The word translated as "saith " is the most common word that means "to say," and "to speak," but it also means "to teach," which seems to be the way Christ uses it more frequently. However, it also has a sense of repeating something heard, which fits here since this verse repeats ideas from earlier verses in parable, especially Matthew 22:4.

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

to -- This word "to" 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.

his  - -- The word translated as "his" is the Greek word commonly translated as third-person pronouns in English.  This pronoun follows the noun so "of his."

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. 

servants,  - The noun translated as "servants" means "slave." It is translated as "servant" to update the Bible.

The -- The word translated as "the" is the Greek definite article, without a noun, it has the sense of "the one." . The Greek article is much closer to our demonstrative pronouns ("this," "that," "these," "those") than the English "the." See this article for more. 

wedding  - The Greek word for "wedding" means a "marriage" and it is the same as the word used earlier in the parable but here it is singular, not plural as it was earlier. The word seems to work like our nuptial/nuptials, the same in singular and plural.

is -- (WP) 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.  It does not appear in this clause but at the end of the verse.

missing "indeed"  -- (MW) The untranslated word  "indeed" here is a particle, which. when used alone. expresses certainty, "truly" and "certainly."

ready,  -- (WP) The "ready" means "at hand," "ready," "prepared," of persons, "ready," "active," "zealous," of the mind, "ready," "bold," and as an adverb, "readily," "willingly." It does not appear in this clause, but at the end of the verse.

but  - The Greek word translated as "but" joins phrases in an adversarial way. Since it always falls in the second position, translating it as "however" often captures its feeling better.

they -- This is from the masculine, plural form of the word.

which -- (IW) There is nothing that can be translated as "which" in the Greek source. It was added because the next verb was translated as active rather than a participle.

were  - -- (WT) This helping verb "were" indicates that the verb is passive. Helping or auxiliary verbs are needed to translate the Greek verb forms into English. It also indicates that the tense is the simple past but this is that past perfect.

bidden  - The term translated as "bidden" is from verb that works like our word "call" means both "to summon" and also "to name." Here it is in the form of a plural noun in the tense of something completed in the past.

were  - The verb "were" is the common form of "to be" in the past tense.

not  - The Greek word translated as "not" is the Greek negative used to deny objective facts, not opinions. It makes a negative statement of fact.

worthy. The word translated here as "worthy" means "counterbalancing." It is the idea of weighing the same as something of equal value. From this comes the idea of "being worthy" or "due," not from inherent worth but because you give value for equal value. Here, they are not worthy of the wedding feast.