What is the difference between "pli" and "plu"?

Question

What is the difference between pli and plu?

Answer 1

From Vortaro:

Pli
Partikulo, esprimanta kvanton aŭ gradon superan al unu alia.
A particle, showing quantity or degree above another.

Examples:

• Milk is more nutritious than wine.
  lakto estas pli nutra, ol vino
• We can do nothing more than be silent.
  ni povas fari nenion pli, ol silenti
• Around ten people are staying, not more.
  restas ĉirkaŭ dek personoj, ne pli

Plu
Cirkonstanca morfemo, montranta la daŭradon k neĉeson de stato aŭ ago.
Cirumstantial morpheme, showing the duration and non-cessation of a state or action.

Examples:

• She wanted to say something more, but could not.
  ŝi volis diri ion plu, sed ŝi ne povis
• I can not go one step more.
  mi ne povas iri unu paŝon plu
• Don't speak (any)more.
  ne parolu plu

Answer 2

• pli is more general "more".
• plu is only for a time duration "longer"

Li ne dormas plu. = He does not sleep anymore / He no longer sleeps

Answer 3

They both mean "more" but in different senses. Pli is used when you would use the -er suffix in English as in bigger, stronger, faster - pli granda, pli forta, pli rapida.

Plu is used as a stand alone as in I can't eat any more, I don't go to school any more, I no more like cheese - mi ne povas manĝi plu, mi ne plu iras al lernejo, mi ne plu ŝatas fromagon.

Answer 4

I was doing a search on this question and I found an interesting blog that does a good job explaining, too.

The blog is called Adventures in Esperanto. Here is some of what it says about the subject:

Pli versus Plu!

Abstractly, the difference is this: “plu” is “further/additionally/more” in relation to time or space. “Pli” means “more” but in relation to size, grade or degree.

So while “plu” is used for something that is continuing or ongoing, “pli” means “more than a certain amount” and as such is used for comparisons.

• La melo ne plu aŭskultas al mi = The badger no longer [/more] listens to me
• La melo estas pli bela ol la kato = The badger is more beautiful than the cat.

This shows that obviously if you use “ne” in conjunction with “plu” is means to not continue etc.

Something a little harder? I found this example on the PMEG page about “plu” using the word “rakonti” = “to relate/tell/narrate”

• Li rakontis plu = He continued his narration (narrated more)
• Li rakontis pli = He related more things (than previously/up until now/than others do/did)

I know this question has been answered, but thought I would share this as another resource.