I have been struggling with adverbs in Esperanto. This morning I was looking up necesas, which I thought should have translated as “is necessary,” and it kind of does. But look at these examples from glosbe.

Via urĝado ne estis necese. You need not have hurried so much.
Mi ne volas dediĉi pli da tempo ol necese en la dompurigado. I don’t want to spend more time cleaning the house than I need to.
Foje ne diri la veron estas necese. It’s sometimes necessary not to tell the truth.
Mi pensas, ke estas necese, ke vi renkontu lin. I think it necessary for you to see him.
Laŭ mi, estus necese, ke vi agu tiel. I think it necessary that you should do so.
Estas ofte necese dependi de la aliaj. It is often necessary to depend upon others.
Mi konsideris necese peti helpon. I found it necessary to get assistance.

You get the idea. How the hell did that transformation happen?  There’s something going on and I’m not quite sure what. What I do know is that I don’t understand adverbs yet. Driving home from an Esperanto meeting, I told an old-time Esperanto speaker about this struggle. His response was it was because I spoke English. En serio? I didn’t buy it. I haven’t struggled with adverbs in Spanish (I struggle with other things), or French. And I certainly don’t remember struggling with them in any other language. Then this morning, I came across this.

238. Adverbs are more widely used in Esperanto than in any other language. The root of every word, and any grammatical termination or affix, the sense of which permits this, can be made into an adverb by adding the adverbial termination E. This facility enables the Esperantist to express in one word, to an unlimited extent, what in other languages often takes two, three, or more words to express adequately. E.g., Tiamaniere = In such a manner. Matene = In the morning. Vespere = In the evening.

Cox, George. The International Auxiliary Language Esperanto Grammar and Commentary (Kindle Locations 2881-2885). . Kindle Edition.

Yay! So, I haven’t been unknowingly a complete language ignoramus all this time. Just mostly. Continuing on through Cox, it’s all good “An adverb answers to a preposition accompanied by a complement… An adverb answers to a preposition accompanied by a complement… N.B.—When an adverb seems to qualify a preposition, it really qualifies an adverbial phrase… Adverbs exercise no influence on the case of nouns, adjectives, or pronouns…

Now here it starts to get interesting for my purposes this morning.

244. Adverbs formed from Prepositions.—When a preposition has no complement, noun or pronoun, the preposition then takes the adverbial termination E. For instance, in the phrase mi staras apud li (I am standing by him); apud here is a preposition because it is followed by its complement li. But if li be omitted, we must alter the sentence, as:—Li staras apude = He is standing by (near).

245. Subject not expressed.—When, in a sentence in Esperanto, there is no noun or pronoun which the adjective can qualify (as in case of verbs in the infinitive, or used impersonally), the adverb is used in Esperanto in place of the adjective. Examples.—Mensogi estas honte (not honta) = To lie is shameful. Estas necese, ke…. = It is necessary that…. Estas bele, varme, malvarme = It is fine, warm, cold. Ne estas atendate, ke…. = It is not expected that…. If, however, a noun or pronoun is expressed, then the adjective is used, as:—La vetero (or, ĝi) estas bela, varma, malvarma = The weather (or, it) is fine, warm, cold.

So here’s the answer. Estas necese (to get do a few of these till I’ve got it down).

One last just to complete the series, at least for me. The reason I put this in is it’s where I first realised that I wasn’t getting adverbs in Esperanto.

245 (a). Participle-Adverbs.—In Esperanto, when the participle relates to the subject (par. 211), but does not qualify it, then the participle takes the adverbial form. For impersonal use see par. 164 (d). Examples.—Legante, ni lernas = In (by, when, while) reading we learn. Starante sur la supro de la monteto, li povis vidi la preĝejon = By standing on the top of the hill, he could see the church. Estante kolera, ŝi ne volis paroli al sia nevo = Being (as she was) angry, she did not wish to speak to her nephew. Malferminte la fenestron, li vidis la amason sur la strato = Having opened (or, after opening) the window, he saw the crowd in (on) the street. Ekrigardinte la libron, ŝi ĝin metis sur la tablon = Having glanced (or, after glancing) at the book, she put it on the table. Forpelite el la urbo, ili rifuĝis en la arbarego = Having been (or, after being) driven from the town, they took refuge in the forest. Batate de la lernejestro, la knabo terure kriegis = Being beaten by the schoolmaster, the boy howled terribly.