在前三期(4月11日)裡，談到不可數名詞是沒有複數形式的，但是常常有人不小心，在某些不可數名詞上加「-s」而犯錯，其中「 experience, equipment, evidence, information」這幾個的錯誤最多。
下面一家裝修商廣告中的「experiences」(經驗)便是一例：
「……our many years of reputable experiences.」
須知，當「經驗」解時，「experience」是不可數名詞，不可以有「-s」：「……our many years of reputable experience(許多年聲譽卓著的裝修經驗)」。當「各種各樣不同經歷」解時，「 experience」是可數名詞，可以有複數「-s」的符號，如：
「Tom could not forget his thrilling experiences in his first trip to Guilin.」
學生作業中，類似的錯誤也不少，如：
① A lot of factors led to students' poor performances. (應為 performance)
② Only people of irreproachable characters can aspire to be good leaders.(應為 character)
③ More and more institutions resort to advanced equipments to assist in the education process.(應為 equipment)
④ Without such knowledges, one would not be able to understand what was seen or heard. (應為 knowledge)
⑤ There is still much room for further improvements.(應為 improvement)
上述這些不可數名詞的錯誤，是不是很熟悉呢?
剛剛談的錯誤是不可有「-s」而用「-s」。另一種錯誤是應該有 「-s」而不用「-s」。雖然後者不像前者這樣麻煩，但是也不難看到。下面三個不同的廣告中便出現了應該有「-s」但漏了「-s」的名詞：
⑥「We are looking for suitable candidate to take up the following positions.」(應為 candidates)。
⑦「Dear customer: Have you been misled by too many brochure?」(應為 brochures)。
⑧「We specialise in rubber tile for factory, office, warehouse, etc.」(應為 rubber tiles, factories, offices, warehouses)
⑥-⑧裡的錯誤顯而易見，只要稍微小心，便不難發現而改正過來。但是，有關不可數名詞加「-s」的錯誤，則較難躲閃，必須加倍警惕才好。其中一個防患辦法是借重量詞，反映不可數名詞之「量」 ，但不改變其形，即不要用「-s」，如：
⑨ There isn't much petroleum in the car.
⑩ John gave some evidence to indicate that the documents had been tampered with.
11. A little knowledge is a dangerous thing.
12. A lot of money has been donated to various charity organisations.
13. Some people today paid little attention to their extravagant acts.