THE COMMA Use a comma before and after non-finite '-ing' clauses This page introduces a 'tricky' use of the comma: non-finite -ing and -ed clauses (sivulauseet). A non-finite clause is a type of clause that cannot stand alone as a sentence (see also subordinate clauses). Unlike a finite clause which contains a verb that has tense and can be conjugated according to person, non-finite clauses have no tense and most commonly contain a present participle (-ing). At the beginning of a sentence, non-finite clauses are similar to both introductory phrases and subordinate clauses in that they all require a comma before the subject of the main clause. Present participles (-ing) are the most common form of non-finite clauses in academic writing. Use a non-finite clause containing a subject and a present participle in the two following cases. 1. One situation or event is occurring at the same time as another. Browsing through the journal 'Science', John was surprised to see so many articles devoted to nanotechnology. (While John was browsing through the journal 'Science', he was surprised to see so many articles devoted to nanotechnology.)   2. A fact is relevant to another fact stated in the main clause. (see also with -ing) While there is some interest in materials recycling technology, most of the research efforts that address recycling appear to be at the design level, with disassembly concerns receiving the highest priority. (While there is some interest in materials recycling technology, most of the research efforts that address recycling appear to be at the design level; of these, disassembly concerns have received the highest priority.)   Use a comma to separate a non-finite -ing clause from the main clause of a sentence, both when it comes before and after the main clause. -ing clause Originating in the high temperatures within the depths of the Earth, geothermic energy is as old as the planet. Geothermic energy is as old as the planet, originating in the high temperatures within the depths of the Earth.   OTHER NON-FINITE CLAUSES Two other less common types of non-finite clauses are those with an infinitive (to do) or past participle (-ed) structure. Note that infinitive clauses need a comma when they come before a main clause, but not when they occur after it. infinitive clause To tackle the above navigational problems, developers of hypertext systems have devised a number of navigational tools. Developers of hypertext systems have devised a number of navigational tools to tackle the above navigational problems.   Non-finite -ed clauses typically modify the subject of the sentence and therefore almost never occur after the main clause. Like infinitive clauses, 'past participle' -ed clauses need a comma to separate them from the main clause when occurring before the main clause, but not after it. -ed clause Based on recent advances in engineering, the molecular laser isotope separation process appears to be the most economical method for uranium enrichment. The molecular laser isotope separation process appears to be the most economical method for uranium enrichment based on recent advances in engineering.

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