Grammatical particle 

Many linguists classify adverbs and prepositions as particles. Conjunctions may also count as particles when they correlate clauses in a sentence.
Interjections expressing attitude, mood, or state of mind may also be classified as particles. Yet another type of particle is the sentence substitutes[?]. Sentence substitutes are sometimes single words that can stand on their own and take the place of a whole sentence, such as "Hello", or "Goodbye", or "Yes".
Finally, the word "to" in an infinitive is considered to be a particle.

As can be seen, the greater number of particles are relatively short words. However, there are also "particle phrases" (adverbial phrases[?]), such as "of course", "as it were", etc., which remain unchanged and separate from other words within the sentence, although they may contain inflected elements, such as "were". Also the so-called tag questions[?], such as "isn't it(?)", "won't he(?)", "doesn't it(?)", etc. which generally go at the end of the sentence, fall under this category, in that they have a reinforcing or reassuring function, or a sentence connection function, or even indicate the mood of attitude of the speaker/narrator.

Also, words such as "the" (the articles[?] with noun); the "to" (in infinitives) and the determiners "more", "most", "less", "least" (in comparatives and superlatives should be regarded as particles as they themselves are not inflected, but belong to other words that are. Yet it must be conceded that they are not isolated in the way particles normally are, since they are part of an over-all grammatical inflection.

However, if particles change into nouns or verbs, they take on the affixes of the inflections of these nouns and verbs, such as in "ifs and buts", or "humming and hawing" (of the interjection "hum").

Grammatical particles are particularly important in colloquial[?] speech, which probably would not be able to convey many special shades of meaning without them. It is the subtle use of particles in phrases such as "now then, what's all this"; "so what"; "you spoke to her, then"?; "anyway, there I was"; "still, it could have been a lot worse"; and many others that make communication in colloquial speech so rich.

List of particles:

• (The first four examples especially reflect a state of mind or attitude on the part of the speaker).
• So (Sentence connector)

  "So" has a defiant element as an answer to a challenging question or statement as in "so what" sentences, such as "I have spoken to your father about you". "So what"! "I have looked into this very closely". "So, does that mean you have found the answer"?

  "So", then, isn't only a sentence connector but it also shows what the speaker's attitude is.

• Well (Sentence connector, as in "Well, that may be true")
• Still (Sentence connector)

  "Still" may be seen as a limiting factor in this example: "We have had a terrible day today". "Still. it could have been a lot worse".

• Yet (Sentence connector)

  "Yet" has a contrasting effect to what has just been said, similarly to "however". "I am seventy years old, and my bones are beginning to creak, yet/however I still enjoy doing some of the things I used to do". So judging by the speaker's state of mind, he doesn' t think he is too old by any means.

• As (Sentence connector)
• Also (Sentence connector)
• Too (Sentence connector)
• Then (Sentence connector, but also Adverb)

  "Then" in this case is a sentence connector but also a sentence modifier in that it modifies the mood in which it was said, meaning "in that case" or "that being so". "You found your wallet then"? Or "go on then".

• Nevertheless (Sentence connector)
• However (Sentence connector)

  "Nevertheless" and "however" are very similar contrast particles often contradicting what has just been said. "I do not like this person one little bit". "However/nevertheless we should work together with him on this project".

• Anyway (Sentence connector)

  "Anyway", too, is used in a similar way but has a limiting or concluding use as in "Anyway, let that be enough" or "anyway, he didn' t stay away long". It has the effect of a summing up or a looking back.

• Even (Adverb, not in the sense of "evenly" but "even the youngest of them")
• Hello, Hallo, or Hullo (Sentence substitute)
• Hi (Sentence substitute)
• Goodbye (Sentence substitute)
• Farewell (Sentence substitute)
• Yes (Sentence substitute)
• No (Sentence substitute)

Coordinating Conjunctions:

• for
• and
• nor
• but
• or
• yet
• so

Some use and/or in writing.

Subordinating Conjunction:

• when
  1. 'They shouted when the team arrived.' The independent clause 'they shouted' joined with 'when' to the independent clause 'the team arrived'.
• Although (Conjunction)

• Ah (Interjection, expressing pleasure, pain, etc.)
• H'm (Interjection, expressing doubt, hesitation, pleasure, etc.)
• Hum (Interjection, expressing again doubt, hesitation, uncertainty, etc.)
• Oh (Interjection, expressing surprise, pain, etc.)

  (There are, of course, many more interjections)

• To (Infinitive, such as "to live", to make", etc.)