Learn Finnish: Monet järjestöt olivat marssineet yhdessä. - Many organizations had marched together.

In Finnish, moni changes form depending on its role in the sentence. Here, the phrase acts as the subject doing the action, so it must be in the nominative plural case: monet järjestöt. You would use the partitive singular monta järjestöä if it were the object of an action, for example 'I saw many organizations'.

How do we get the form monet from the base word moni?

The word moni (many) has an irregular stem. When adding most endings, the final -i changes, giving us the stem mone-. To make the nominative plural, you just add the standard plural -t to this stem, resulting in monet.

How is the verb form olivat marssineet constructed to mean 'had marched'?

This is the pluperfect (past perfect) tense. It uses the past tense of the helper verb olla (here, olivat to match the plural 'they' subject) combined with the past participle of marssia. Because the subject monet järjestöt is plural, the participle also takes the plural ending -neet, giving us marssineet.

What is the literal translation of the word yhdessä?

It literally means 'in one'. It is the number yksi (one) put into the inessive case (-ssä). Over time, this case form became the standard fixed adverb for 'together'.