Size, length & amount
How big or long something is and how much of it there is: the size and quantity scales, plus nagai for length and for time.
ookii
polite ookii desubig, large, loud
大きい おおきい 大きいです
The size of things and people, loudness (ookii koe = a loud voice) and how big a matter is; before nouns, ookina is just as common.
kono kutsu, chotto ookii
These shoes are a bit big.
この靴、ちょっと大きい
kono kutsu wa chotto ookii desu
These shoes are a little big.
この靴はちょっと大きいです
For 'a lot of', use ooi or takusan, not ookii.
Learn alongside: chiisai
chiisai
polite chiisai desusmall, little
小さい ちいさい 小さいです
The size of things, quiet voices (chiisai koe) and childhood (chiisai koro = when I was little); before nouns it is also chiisana.
kono kutsu, chotto chiisai
These shoes are a bit small.
この靴、ちょっと小さい
kono kutsu wa chotto chiisai desu
These shoes are a little small.
この靴はちょっと小さいです
chiisana goes only before a noun (chiisana mise); at the end of a sentence it is always chiisai.
ooi
polite ooi desumany, a lot
多い おおい 多いです
Says there are many or a lot of something, or that something happens often (machigai ga ooi); it works after the noun (hito ga ooi) and not normally in front of it.
kyou, hito ga ooi ne
There are a lot of people today.
今日、人が多いね
kyou wa hito ga ooi desu ne
There are a lot of people today.
今日は人が多いですね
Not 'ooi hito' for 'many people'; say takusan no hito instead.
Learn alongside: sukunai
sukunai
polite sukunai desufew, not much
少ない すくない 少ないです
Says there are few or not much of something; the opposite of ooi, with the same after-the-noun pattern (hito ga sukunai).
kyou, hito ga sukunai ne
There aren't many people today.
今日、人が少ないね
kyou wa hito ga sukunai desu ne
There aren't many people today.
今日は人が少ないですね
Not sukoshi (a little, B): sukunai describes an amount, sukoshi gives one.
nagai
polite nagai desulong (length or time)
長い ながい 長いです
Describes length (hair, lines, roads) and, just as often, duration: a long film, meeting or wait. nagai aida means 'for a long time'.
kono eiga, chotto nagai ne
This film's a bit long, huh.
この映画、ちょっと長いね
kono eiga wa chotto nagai desu ne
This film is a little long, isn't it?
この映画はちょっと長いですね
nagaku natte gomen = sorry this got long (a message or a talk); the opposite is mijikai (short).