A morpheme is a basic unit of meaning. Some English morphemes, such as teach and nation, can be independent words, but other morphemes are only parts of words, such as inter- and -er, which cannot be used alone. 語素是語義的基本單位。英語的某些語素（例如：teach 和 nation）可以獨立使用，但有些語素只能當詞語的一部分（例如：inter- 和 -er）：
teacher
|
international
|
INTER-
|
|
TEACH
|
NATION
|
-ER
|
-AL
|
Unlike many other European languages, English only has two tense morphemes: present (PR) and past (PA). PR only appears as -s after 3rd person singular verbs; in other places, is is not visible [Ø]. In written form, PA usually appears as -ed, but it has many other shapes. 有別於其他歐洲語言，英語只有兩個時態語素：現在式 PR 和過去式 PA。在單數第三人稱動詞之後，PR 用 -s 形式；其他情況則是用零變體 [Ø]。PA的書面形式通常是 -ed，但也有許多其他的形式。
Just like other morphemes, tense has a meaning. Here are some possible meanings of PR contrasted with PA. 就像其他的語素一樣，時態具有意義。底下是一些可能的意義：
1
|
2
|
3
|
|
PR
(present)
|
repeated event
重複發生的事情
(general truth)
|
true
(dramatic)
|
now
|
PA
(past)
|
one
time event
單次發生的事情
(specific)
|
unreal
|
then
|
Chinese has no tense morphemes, so Chinese students are often not sure which tense to use. 漢語沒有時態語素，所以中國學生有時無法確定該用哪一個時態：
Cyclones vs. This Cyclone
1 Plural nouns with no determiner (cyclones, tornadoes) usually refer to something that is generally true, so the verb should be PR (begin = BEGIN + PR [Ø])
不加限定詞的複數名詞通常指一般的真理，所以動詞應該加現在式。
"Tornadoes begin as dark clouds" 應該翻譯成『龍捲風的形成通常是烏雲』
2 A singular noun (cyclone) with a determiner (the, this, that, my, your etc.) refers to a particular case, so the verb should be PA (began = BEGIN + PA [*])
加限定詞的單數名詞指個別例子，所以動詞是應該加過去式。
"This cyclone was no different" 應該翻成『這一次的龍捲風不例外』
More examples below:
