The basic form is "mały", so there's a "ł" already. I can't explain why mały becomes mali, but it seems it's common for in mixed plural form (not sure if it's the correct name)
- duży chłopiec → duzi chłopcy; duża dziewczynka → duże dziewczynki
- sprytny (smart) chłopiec → sprytni chłopcy; sprytna dziewczynka → sprytne dziewczynki
- miły (nice, kind) chłopiec → mili chłopcy; miła dziewczynka → miłe dziewczynki
"Ł" doesn't like being followed by "i", so it then turns into "L". Words with "LY" are very rare (for example, "Lykantropia"). Words with "ŁI" also, maybe even not a single one exists.
There was a great comment on "Źli ludzie." by HelioLBS which explains the l-question: "Well, in Polish (and other languages) there's what is called "a phonological agreement". Soft consonants go with soft ones and hard consonants go with hard ones. If I'm not mistaken, "l" is considered "soft" and "ł" is considered "hard". Nominative, singular, masculine adjectives usually end in "-y", which agrees phonologically with hard consonants, for instance "zły". To form its plural, we need to drop the "-y" and replace it with its soft version "-i", but the latter only agrees with soft consonants, so we need to drop the "-ł-" and replace it with its soft version "-l-", but "z" is not soft, so we also need to replace it with its soft version "ź". Then we are left with "źli", in which all three sounds agree in phonological softness. Please, everyone, feel free to tweak this explanation; I'm not a 100% sure I explained correctly."
It's more the opposite question you should concern yourself with, why does "ł" become "l" in the masculine form, because "ł" is in the basic form of the adjective "mały" (the basic form given is the masc. sing. Nom.).
"The masculine personal plural adjective ending is -y/-i and the preceding consonant is softened: dobry → dobrzy, ładny → ładni, miły → mili, wielki → wielcy, drogi → drodzy; for more examples, see below.
Swan, Oscar (2008-10-12). Polish Verbs & Essentials of Grammar, Second Edition (Verbs and Essentials of Grammar Series) (Kindle Locations 780-782). McGraw-Hill Education. Kindle Edition.
As you can see the third example is almost exactly the same word, save one vowel change.
Without explanation it feels like puzzeling in stead of learning a language. So puzzeling I find that the adjectives before nominative plural nouns are formed like so: -y/-i for male personal, and -e for male non-personal, female en neuters (not taking in account some some extra letter changes) Can anyone confirm or correct?
It would also be a nice timesaver if we could get a hint on the adjectives for plural nouns in Accusative and Instrumental.
You have to remember the masculine/neuter/feminine plurals and non-plurals. Then you would understand more. Try taking notes in a journal, it really helps.
There are good tutors too if you'd like a one-on-one conversation with someone instead of learning off of a website.
Thanks Madcat, for your offer. Next week I'm gonna start all over with my son. We'll now use additional sources for our information.
Any notes on plural endings for adjectives? I know singular endings are y, a, and e for masc, fem, and neut respectively. For plurals, is it i, and e, for masc, and fem respectively? + what's for neut? Thanks in advance for help folks
In plural you don't have masculine/feminine/neuter. There are 'only' two plurals. Sometimes they are called masculine and feminine, but although that seems simple and tempting, it's just not true. Their real names are complicated, but at least descriptive.
The first one is 'masculine personal plural' - generally, it's used for 'groups of people including at least one man'. So as "chłopcy" are men, they are obviously masculine personal.
The second one is 'not masculine-personal plural' - and it's used for everything else. All feminine nouns, all neuter nouns, and the masculine nouns that don't denote people.