The -le / -ले particle in Nepali is attached to the subject (noun or pronoun) of a sentence with a transitive verb in the most common of the past tenses: Simple past (used as example in the video), Present perfect and Past perfect. Other past tenses do not need the -le particle: Past habituous and past continuous.
To know with which verbs to use -le, you first have to understand the difference between transitive verbs and intransitive verbs. Which is probably the most difficult part. FOr English or German speakers there is no need to intuitively know the difference between those two types of verbs: It makes no difference for the syntax of the sentence (other than using direct objects or not – but that is more a semantic issue, I feel).
A intransitive verb is a verb that can NOT take a direct object.
“I go.” [Subject + verb]
-> Here you cannot ask: >You go what?”
A transitive verb is a verb that takes a direct object in a sentence.
“I eat my lunch” [Subject + verb + direct object[possesive pronoun + noun]]”
-> Here you can ask: >You eat what?< For the Nepali example we focus on the third person singular in the simple past tense
उ गयो [u gayo] – He went.
केटा गयो [keTaa gayo] – The boy went.
Other intransitive verbs in Nepali are e.g. आउनु [aaunu] – to come, बस्नु [basnu] – to sit, हाँस्नु [haa~snu] – to laugh, पिट्नु [piTnu] – to beat
उस्ले खाना खायो [usle khaanaa khaayo] – He ate his lunch/dinner
केटाले खाना खायो [keTaale khaanaa khaayo] – The boy ate his lunch.
– Even if a transitive verb is used without a direct object, in Nepali it will still be treated as transitive, therefore you would say: केटाले खायो [keTaale khaayo] – the boy ate.
– There are many verbs in Nepali that combine गर्नु [garnu] with a noun. Like for example काम गर्नु [kaam garnu] which means “to work”. And even though those verbs might be intransitive sometimes in English, in Nepali all those words need to be treated as transitive (and the direct object being the noun that is combined with गर्नु) and they will therefore need the -le particle attached to the subject in the specified past tenses!