Linguists usually draw a distinction between content words, those words whose meaning is best described in a dictionary and which belong in open sets so that new ones can freely be
added to the language, and function words, words with little inherent meaning but with important roles in the grammar of a language. Typically the content words are nouns, verbs, adjectives and some adverbs, while function words are pronouns, conjunctions, prepositions, auxiliary verbs, and some adverbs.
Some of these function words are homonyms of content words, so that only the context can tell you which meaning is intended. Among the adverbs these include BACK, JUST and STILL. Among the auxiliary verbs are CAN, DOES, MAY MIGHT and MUST. Among the prepositions/conjunctions are DOWN, ROUND and TILL, and among the determiners is MINE. There will be more of these overlaps if you use software which standardises input by stripping punctuation, in which cases items like CAN'T, HE'LL, I'LL, SHE'D and SHE'LL will turn into CANT, HELL, ILL, SHED and SHELL.
The lists below were originally produced for the purpose of masking selected parts of speech in the text game ECLIPSE by John and Muriel Higgins.
Adverbs other than manner adverbs and omitting the funny legal ones.
AGAIN AGO ALMOST ALREADY ALSO ALWAYS ANYWHERE BACK ELSE EVEN EVER EVERYWHERE FAR HENCE HERE HITHER HOW HOWEVER JUST NEAR NEARBY NEARLY NEVER NOT NOW NOWHERE OFTEN ONLY QUITE RATHER SOMETIMES SOMEWHERE SOON STILL THEN THENCE THERE THEREFORE THITHER THUS TODAY TOMORROW TOO UNDERNEATH VERY WHEN WHENCE WHERE WHITHER WHY YES YESTERDAY YET
(The problem in this section is the adverbs of frequency. There is no clearcut division between the common words never, often and sometimes, which seem to belong to the function
Auxiliary verbs (including contractions)
Prepositions/Conjunctions (one category since there is some overlap)
word class, and words like frequently, occasionally, or seldom, which would usually be described as content words although they occupy the same area of meaning.)
AM ARE AREN'T BE BEEN BEING CAN CAN'T COULD COULDN'T DID DIDN'T DO DOES DOESN'T DOING DONE DON'T GET GETS GETTING GOT HAD HADN'T HAS HASN'T HAVE HAVEN'T HAVING HE'D HE'LL HE'S I'D I'LL I'M IS I'VE ISN'T IT'S MAY MIGHT MUST MUSTN'T OUGHT OUGHTN'T SHALL SHAN'T SHE'D SHE'LL SHE'S SHOULD SHOULDN'T THAT'S THEY'D THEY'LL THEY'RE WAS WASN'T WE'D WE'LL WERE WE'RE WEREN'T WE'VE WILL WON'T WOULD WOULDN'T YOU'D YOU'LL YOU'RE YOU'VE
ABOUT ABOVE AFTER ALONG ALTHOUGH AMONG AND AROUND AS AT BEFORE BELOW BENEATH BESIDE BETWEEN BEYOND BUT BY DOWN DURING EXCEPT FOR FROM IF IN INTO NEAR NOR OF OFF ON OR OUT OVER ROUND SINCE SO THAN THAT THOUGH THROUGH TILL TO TOWARDS UNDER UNLESS UNTIL UP WHEREAS WHILE WITH WITHIN WITHOUT
Determiners/Pronouns (omitting archaic THOU, THEE, etc)
A ALL AN ANOTHER ANY ANYBODY ANYTHING BOTH EACH EITHER ENOUGH EVERY EVERYBODY EVERYONE EVERYTHING FEW FEWER HE HER HERS HERSELF HIM HIMSELF HIS I IT ITS ITSELF LESS MANY ME MINE MORE MOST MUCH MY MYSELF NEITHER NO NOBODY NONE NOONE NOTHING OTHER OTHERS OUR OURS OURSELVES SHE SOME SOMEBODY SOMEONE SOMETHING SUCH THAT THE THEIR THEIRS THEM THEMSELVES THESE THEY THIS THOSE US WE WHAT WHICH WHO WHOM WHOSE YOU YOUR YOURS YOURSELF YOURSELVES
Numbers
BILLION BILLIONTH EIGHT EIGHTEEN EIGHTEENTH EIGHTH EIGHTIETH EIGHTY ELEVEN ELEVENTH FIFTEEN FIFTEENTH FIFTH FIFTIETH FIFTY FIRST FIVE FORTIETH FORTY FOUR FOURTEEN FOURTEENTH FOURTH HUNDRED HUNDREDTH LAST MILLION MILLIONTH NEXT NINE NINETEEN NINETEENTH NINETIETH NINETY NINTH ONCE ONE SECOND SEVEN SEVENTEEN SEVENTEENTH SEVENTH SEVENTIETH SEVENTY SIX SIXTEEN SIXTEENTH SIXTH SIXTIETH SIXTY TEN TENTH THIRD THIRTEEN THIRTEENTH THIRTIETH THIRTY THOUSAND THOUSANDTH THREE THRICE TWELFTH TWELVE TWENTIETH TWENTY TWICE TWO
The complete alphabetical list of 321 items
A ABOUT ABOVE AFTER AGAIN AGO ALL ALMOST ALONG ALREADY ALSO ALTHOUGH ALWAYS AM AMONG AN AND ANOTHER ANY ANYBODY ANYTHING ANYWHERE ARE AREN'T AROUND AS AT BACK ELSE BE BEEN BEFORE BEING BELOW BENEATH BESIDE BETWEEN BEYOND BILLION BILLIONTH BOTH EACH BUT BY CAN CAN'T COULD COULDN'T DID DIDN'T DO DOES DOESN'T DOING DONE DON'T DOWN DURING EIGHT EIGHTEEN EIGHTEENTH EIGHTH EIGHTIETH EIGHTY EITHER ELEVEN ELEVENTH ENOUGH EVEN EVER EVERY EVERYBODY EVERYONE EVERYTHING EVERYWHERE EXCEPT FAR FEW FEWER FIFTEEN FIFTEENTH FIFTH FIFTIETH FIFTY FIRST FIVE FOR FORTIETH FORTY FOUR FOURTEEN FOURTEENTH FOURTH HUNDRED FROM GET GETS GETTING GOT HAD HADN'T HAS HASN'T HAVE HAVEN'T HAVING HE HE'D HE'LL HENCE HER HERE HERS HERSELF HE'S HIM HIMSELF HIS HITHER HOW HOWEVER NEAR HUNDREDTH I I'D IF I'LL I'M IN INTO IS I'VE ISN'T IT ITS IT'S ITSELF JUST LAST LESS MANY ME MAY MIGHT MILLION MILLIONTH MINE MORE MOST MUCH MUST MUSTN'T MY MYSELF NEAR NEARBY NEARLY NEITHER NEVER NEXT NINE NINETEEN NINETEENTH NINETIETH NINETY NINTH NO NOBODY NONE NOONE NOTHING NOR NOT NOW NOWHERE OF OFF OFTEN ON OR ONCE ONE ONLY OTHER OTHERS OUGHT OUGHTN'T OUR OURS OURSELVES OUT OVER QUITE RATHER ROUND SECOND SEVEN SEVENTEEN SEVENTEENTH SEVENTH SEVENTIETH SEVENTY SHALL SHAN'T SHE'D SHE SHE'LL SHE'S SHOULD SHOULDN'T SINCE SIX SIXTEEN SIXTEENTH SIXTH SIXTIETH SIXTY SO SOME SOMEBODY SOMEONE SOMETHING SOMETIMES SOMEWHERE SOON STILL SUCH TEN TENTH THAN THAT THAT THAT'S THE THEIR THEIRS THEM THEMSELVES THESE THEN THENCE THERE THEREFORE THEY THEY'D THEY'LL THEY'RE THIRD THIRTEEN THIRTEENTH THIRTIETH THIRTY THIS THITHER THOSE THOUGH THOUSAND THOUSANDTH THREE THRICE THROUGH THUS TILL TO TOWARDS TODAY TOMORROW TOO TWELFTH TWELVE TWENTIETH TWENTY TWICE TWO UNDER UNDERNEATH UNLESS UNTIL UP US VERY WHEN WAS WASN'T WE WE'D WE'LL WERE WE'RE WEREN'T WE'VE WHAT WHENCE WHERE WHEREAS WHICH WHILE WHITHER WHO WHOM WHOSE WHY WILL WITH WITHIN WITHOUT WON'T WOULD WOULDN'T YES YESTERDAY YET YOU YOUR YOU'D YOU'LL YOU'RE YOURS YOURSELF YOURSELVES YOU'VE