The fourth letter in weiße is not a syllabi; it is a letter. It's name is the Eszett or scharfes S (sharp S).
You can, in all likelihood, type ß--as well as ä, ö, und ü--you just don't know how. But if you will read through this article at the duolingo.wiki, then you should be able to figure out how to remedy that.
There are two basic types of adjectives in German:
1.) Predicate adjectives, i.e. adjectives used after verbs such as "sein" (to be) and "werden" (to become). They do not get an ending. Ex. Der Tisch ist weiß. (The table is white). Die Tische sind weiß (The tables are white). Die Katze ist weiß. (The cat is white), etc.
2.) Attributive adjectives, i.e. adjectives before nouns (e.g. "white tables", "the nice man", "a black cat", "my long shirt", etc.). The get an ending. The ending depends on three factors:
a.) the type of article word used with the noun the adjective refers to (a, the, my, no article ...)
b.) the gender/number of the noun the adjective refers to (masculine, feminine, neuter OR plural)
c.) the case of the noun the adjective refers to.
E.g. in the sentence "I like white tables", the adjective "white" refers to the noun "tables" (Tische), which is:
a.) not accompanied by an article (= the so-called strong inflection for adjectives is used)
c.) accusative (because it's the direct object, and almost all direct objects are in the accusative case).
The adjective ending for strong inflection, plural, accusative is -e: weiße.
See this table:
For an alternative explanation of adjective endings, see:
The best part is: English mirrors the attributive/predicate categories for adjectives. (We also have Nominal adjectives, see https://en.wikipedia.org/wiki/Nominalized_adjective. Ich kenne nicht ob Deutsche hat dasselbe.)
Yes, that's possible. I come from a region where the "i" is sometimes pronounced a bit like an "ü", I think.
I'm having trouble understanding why it's "weisse" and not "weissen". Since Tische is plural it should take the -en ending for adjectives, no?
If there is an article word (a, the, my, etc.), attributive adjectives (= adjectives before nouns) indeed always get the ending -en in the plural.
However, in this sentence there is no article word, so the so-called "strong inflection" for adjectives is used. In the strong inflection, there are different endings for plural adjectives depending on the case. In the sentence "Ich mag weiße Tische", "weiße Tische" is the direct object. For almost all direct objects, the accusative case is used in German. The ending for strong inflection, plural, accusative is -e: weiß-e.
See this table:
Nooooo @Flor in the accusative, only the masculine adjective takes -en! That is, if theres no article. Weissen Tisch (M). Weisse Frau (F). Weisse Madchen (N). Weisse Tische (Pl).
But if u do use an article, it's different, and different again depending on whether you use a definite or indefinite article.
And this is just for the accusative case.
I avoided learning adjective endings for ages, hoping I'd just see patterns on Duo. But it was impossible. I just read the wikipedia page (for some reason I can't put the link?!) and the idea was clear. I took screen shots of their 3 tables and i still refer to them so not learnt by heart ...yet
DL gives "boards" as a hint, but the only context I can think of where "Tisch" could be translated as "board" is the idiom "unter den Tisch fallen" (literally: to fall under the table, normal translation: to go by the board).