It’s easy enough to explain what a noun, verb, adjective, or adverb is, but defining participle is not so easy. Dictionaries typically say a participle combines traits of an adjective and a verb, but that explanation isn’t very clear. It also overlooks the fact that participles can be used as other parts of speech — such as adverbs in Russian and Hungarian. In English, the present participle can be used as a noun, though traditionally in that role it’s called not a participle but a gerund.
In English, each verb is associated with just two participles, past and present. The present (or “active”) participle is perfectly regular except for spelling, always formed by addition of -ing to the infinitive. The past (or “passive”) participle is usually, but not always, the same as the past tense. Examples of present/past participles include being/been, doing/done, eating/eaten, loving/loved.
Participles in Esperanto come in much greater variety. Each verb has three corresponding active participles identified by the endings -inta, -anta, and -onta. In addition, transitive verbs (those that take objects) also have a trio of passive participles ending in -ita, -ata, and -ota. The difference between active and passive participles is that active participles go with the subject, and passive participles go with the object of the verb. (That’s why only transitive verbs have passive participles.) For example, the phrase Li amas ŝin implies that li estas amanta and ŝi estas amata.
In addition to three or six adjective participles for a given verb, Esperanto allows participles to serve as nouns and adverbs. Given all the possible forms this implies, a student can be forgiven for thinking that English, with its two participles, is simpler.
Of course once you actually start putting participles to use, English turns out to be not so simple after all. The active/passive distinction seems simple enough in the sentences It was eating and It was eaten. But what about It has eaten versus It was eaten? Apparently not just the participle but the associated verb can determine whether the meaning is active or passive. Moreover, while you can say It is eating, you would not normally say of an action in progress, It is eaten but rather It is being eaten. Native speakers of English aren’t conscious of how complicated this system is until they try to write down all the rules.
Esperanto participles, on the other hand, are richly expressive but pretty straightforward once you understand the basic ideas of how they work. Here’s a suggested approach for introducing participles one concept at a time:
Start with the word Esperanto itself. Students have probably already been told what it means, so you can treat -anto as a simple suffix. You can then mention other examples of words ending in -anto, such as manĝanto and amanto.
Speaking of amanto gives you a reason to bring up the corresponding passive form amato. From there it’s an easy step to the corresponding adjectives ending in -anta and -ata.
Having covered the adjective versions, the next step is adverbs, such as amante (“lovingly”). This is a good time to bring up something very common in Esperanto, the participial adverb leading off a sentence, as in Amante mi rigardas vin.
Now you can illustrate adding words to make an adverbial phrase. To make it seem more natural, you can start with an English expression (for instance, Being loved by you, I’m happy) and its Esperanto translation (Estante amata de vi, mi feliĉas). You can then show how to say the same thing more concisely: Amate de vi, mi feliĉas.
Once the student is comfortable with an adverbial phrase involving a participle, you can bring up the novel idea of a participle taking an object like a verb would, as in Amante vin, mi sopiras. Students may have trouble getting their minds around the idea of something other than a verb taking a direct object, so this a good time to stop and explain the mixed properties of participles. I think it’s easier to explain something students have already seen than to introduce the abstract idea before they have any practical familiarity with the topic.
Now, having broken the news of participles having verb-like properties, it’s natural to show that participles can refer to the past, future, and present by using the same set of vowels already familiar from -is, -as, and -os. As always, practical examples are very helpful, such as: Leginte vian leteron, mi decidis telefoni vin.
It’s worth saying something about compound tenses. We’re so used to them in English that it’s natural to look for an equivalent in Esperanto. But Esperanto isn’t English, and students should know that where an English speaker would use a compound tense, in Esperanto it’s much more typical to use a simple tense, possibly together with an adverb for clarity or emphasis. The usual equivalent for I’m thinking isn’t Mi estas pensanta but simply Mi pensas, and while I’ve (already) eaten could be translated Mi (jam) estas manĝinta, in practice one would more likely say: Mi jam manĝis.
Still, there are certainly cases when the combination of esti and a participle is the best choice to convey a precise meaning. For example, the best translation of the English pluperfect construction I had eaten is probably Mi estis manĝinta.
Since the verb esti can take any of its forms — esti, estu, estus, estis, estas, estos — and the participle itself can be past, present, or future, there are quite a lot of possible combinations. It helps to think of them not as a complicated set of compound tenses, but as what they actually are: the verb to be linking the subject with a descriptive adjective. E.g., manĝonta, being an active future participle, means “yet to eat,” so Mi estis manĝonta means “I was yet to eat,” Mi estas manĝonta means “I am yet to eat,” Mi estos manĝonta means “I will be yet to eat,” Mi estus manĝonta means “I would have been yet to eat,” and so on.
There are still some subtle points that could be brought up in a more advanced course, but as a practical matter, this is the bulk of what students need to understand about participles and participial phrases. Beyond this it’s mainly a matter of experience and practice.