Learn English – What’s a word for an instance in which one has an opinion about something without having tried it

The point that a word should make is that it has to be an adequate symbol for what it represents.

This is, in essence, arbitrary and pragmatic and what ever work (as a symbol) will make its way into memories and experience of individuals, then a subculture (jargon) and then culture (spreading from common spoken use to use in periodical publications to the moment these words are added to dictionaries).

It can follow patterns from Greek or Latin, and you will find many example in this and last century — we had to invent many new words to deal with advance of information technology.

If you read up on neologism you will find other ways of constructing new words mentioned — combining existing words (regardless of etymology), abbreviating, rhyming, etc..

• urban dictionary almost exclusively shows neologisms (even fictional)

• Here you can see new words in journals

• You can also look at lists of words added to a dictionary, such as this sample from Merriam-Webster

As you examine these lists you will see progression from less adopted words to more standard words and you might see some patterns that make them accepted into the language.

EDIT:

• There is polycephaly - which refers to general condition of having more then one head
• In case of words prefixed with poly-, the usual counterpart is mono- and so your best bet is monocephaly

After I constructed the word, I looked it up and it exists:

mon·o·ce·phal·ic

Bearing one flower head, as in the scape of a dandelion.

It turns out that the OED does attest a verb (and resulting noun) disesteem. They suggest that it may be related to its French cognate désestimer from the 16^th century, or to the equivalent Italian version, disestimare. I get the feeling these were used more way back when than they are now.

The OED gives to disesteem as a transitive verb whose first (and only non-obsolete) sense is:

To regard with the reverse of esteem; to hold in low estimation, regard lightly, think little (or nothing) of, slight, despise.

• 1594 Daniel Cleopatra Ded., ― Ourselves, whose error ever is Strange notes to like, and disesteem our own.
• 1629 Lynde Via tuta 195 ― The authority of Prelates would bee disesteemed.
• 1735 Wesley Wks. (1872) XIV. 208 ― Nor will he at all disesteem the precious pearl, for the meanness of the shell.
• 1868 Helps Realmah (1876) 262 ― Thinking that he had somehow or other offended Ellesmere, or was greatly disesteemed by him.

That’s the verb; also per OED, the noun is:

The action of disesteeming, or position of being disesteemed; want of esteem; low estimation or regard.

• 1603 Florio Montaigne (1634) 66 ― The Turkes, a nation equally instructed to the esteeme of armes, and disesteeme of letters.
• 1670 Milton Hist. Eng. ɪ. Wks. (1851) 1 ― Disesteem and contempt of the public affairs.
• 1697 Dryden Virg. Past. Pref. (1721) I. 76 ― Pastorals are fallen into Disesteem.
• 1754 Edwards Freed. Will ɪᴠ. i. 195 ― Their Worthiness of Esteem or Disesteem, Praise or Dispraise.
• 1810 Bentham Packing (1821) 91 ― Whatever tends to bring a man in power into ‘disesteem’.
• 1884 Pennington Wiclif ii. 32 ― The prevailing disesteem in which the Scriptures were held.

This Google N-gram suggests that while not quite unknown, that it has even less currency than do disparage or deprecate:

Gosh, they were certainly more negative back in the 19^th century, weren’t they now? :)

Sure, it’s kind of old-fashioned, but it does seem to exactly match your desired sense. It’s probably better than the ^{_{(only deceptively, as it turns out)}} modern-sounding disrespect, and doesn’t carry the overtones of active disapproval that disparage does.