Five jobs, and nothing else
A comma is not a breath mark. It has a short, closed list of jobs, and a comma that is not doing one of them is an error.
- Join. Comma $+$ a coordinating conjunction (for, and, nor, but, or, yet, so) between two independent clauses.
- Introduce. After an introductory element — a dependent clause, a participial phrase, a long prepositional phrase, a transition.
- Enclose. A matching pair around a supplement: material the sentence does not need.
- Separate a list. Between the items of a series of three or more, including before the final and.
- Separate coordinate adjectives. Between adjectives that modify the noun independently.
The default is no comma. Faced with a slot, do not ask whether a comma sounds right. Ask which of the five jobs it would be doing. If none, delete it.
Học sinh Việt hay đặt dấu phẩy theo nhịp đọc của tiếng Việt — chỗ nào hụt hơi thì phẩy. Tiếng Anh viết không hoạt động như vậy. Dấu phẩy chỉ có năm việc; không thuộc việc nào thì phải bỏ. Đảo ngược thói quen này là phần lớn số điểm của nhóm câu dấu phẩy.
Job 1 and job 2: joining and introducing
After more than a decade of failed attempts to synthesise the compounda graduate student produced it by accident.
- ,
- ;
- :
- (no punctuation)
Everything before the slot is a prepositional phrase, not a clause, so a semicolon and a colon are both impossible — each needs an independent clause on its left. An introductory element of this length takes a comma before the main clause. Answer (A).
The joining job is the one students over-apply, because a comma before and looks safe. It is safe only when a full clause follows.
The engraver cut the plate in Amsterdamsold impressions of it in London for the next thirty years.
- , and
- and
- ; and
- , he
Sold impressions of it in London has no subject of its own; it shares the engraver with the first verb. This is a compound predicate, not a second clause, so job 1 does not apply and no comma belongs before and, which rules out (A). (C) puts a semicolon in front of material that cannot stand alone. (D) supplies a subject but joins the resulting clause with a bare comma, a splice. Answer (B).
Kiểm vị ngữ ghép bằng một câu hỏi: phần sau and có chủ ngữ riêng không? Không có chủ ngữ riêng thì tuyệt đối không phẩy trước and. Có chủ ngữ riêng, và phần đó đứng riêng thành câu được, thì bắt buộc phải có phẩy. Đây là cặp bẫy được ra đề nhiều nhất trong cả nhóm.
Job 3: the matching pair, and the essential test
A supplement is material that can be deleted without breaking the sentence. It is enclosed by a matching pair. Material that cannot be deleted — because it identifies which one — is essential and takes no punctuation at all.
Her 1970 paperwritten with Kent Fordmeasured rotation curves that visible matter could not explain.
- ,\ …\ ,
- (none)\ …\ (none)
- ,\ …\ (none)
- (none)\ …\ ,
Delete written with Kent Ford and the sentence still stands, so the phrase is a supplement and needs a pair. A single comma at one end only, as in (C) and (D), cuts the subject off from its verb; (B) leaves a modifier jammed between them with no boundary at all. Answer (A).
Sculpturesthat were carved from a single block of stonewere far less likely to survive transport.
- ,\ …\ ,
- ,\ …\ (none)
- (none)\ …\ (none)
- (none)\ …\ ,
Delete the clause and the sentence claims that sculptures in general rarely survived transport — a different and false claim. The clause is doing identifying work, and a that clause is always essential, so it takes no punctuation. Answer (C).
Phép thử duy nhất cần dùng: xoá cụm đó đi rồi đọc lại. Nếu câu vẫn đủ nghĩa như cũ, cụm đó là thông tin xen và phải được kẹp bằng một cặp khớp. Nếu xoá xong câu đổi nghĩa hoặc không còn biết đang nói về cái nào, cụm đó là thông tin xác định và không được có dấu phẩy nào cả. Riêng mệnh đề mở đầu bằng that thì luôn luôn là xác định.
Jobs 4 and 5: lists and adjectives
The catalogue lists the artist's birthplacethe dates of her two trips to Italyand the provenance of every surviving canvas.
- ,\ …\ ,
- ;\ …\ ;
- ,\ …\ (none)
- (none)\ …\ ,
Three items, none of which contains an internal comma, so ordinary commas separate them and the serial comma before and is required. Semicolons are reserved for items that already carry commas. Answer (A).
Adjectives take a comma only when each modifies the noun independently. Two tests agree: insert and between them, or swap their order. If either move works, they are coordinate.
The dealer offered the museum a smallRoman bronze lamp said to have come from Pompeii.
- ,
- and
- (no punctuation)
- ;
A small and Roman bronze lamp is impossible, and so is a Roman small bronze lamp. The adjectives stack rather than coordinate: Roman bronze lamp is the unit, and small modifies the whole of it. No comma. Answer (C).
Tính từ trong tiếng Anh chia hai loại. Loại ngang hàng cùng bổ nghĩa thẳng cho danh từ — chen được and vào giữa, đảo được thứ tự — thì có dấu phẩy. Loại chồng tầng thì tính từ đứng trước bổ nghĩa cho cả cụm đứng sau (small bổ nghĩa cho Roman bronze lamp), chen and vào là hỏng, và tuyệt đối không có dấu phẩy. Cứ thử chen and trước khi quyết định.
Where a comma is always wrong
- Between a subject and its verb, however long the subject grows.
- Between a verb and its object or complement.
- Between a preposition and its object.
- Before that introducing a clause.
The persistence of oral traditions among communities separated by thousands of kilometres of open oceansuggests a common origin.
- ,
- (no punctuation)
- ;
- —
The subject is The persistence, and everything through ocean modifies it; the verb is suggests. A single mark of any kind between them is an error, and (C) would also demand a clause on each side. Answer (B).
Field notebooks from the 1899 expedition recorddaily temperature readings, ice conditions, and the behaviour of the dogs.
- ,
- :
- ;
- (no punctuation)
Record is the verb and the list is its object. Nothing separates them — not a comma, and not a colon either, since the material to the left of a colon must be able to stand alone and Field notebooks… record cannot. Answer (D).
Câu càng dài, chủ ngữ càng bị đẩy xa động từ, và mắt càng muốn đặt một dấu phẩy ở chỗ nghỉ. Bốn điều cấm ở trên không có ngoại lệ nào theo độ dài. Cách chữa: rút gọn câu về đúng ba từ — chủ ngữ, động từ, tân ngữ — rồi hỏi có ai đặt phẩy vào đó không.