Coordinating conjunctions link words, phrases, or clauses. The units being joined by a coordinating conjunction must be parallel in grammatical structure and importance. Some common coordinating conjunctions are and, but, or, for, nor, so, and yet.
Half the world's population of nearly six billion people prepare their food
and heat their homes with coal and the
traditional biomass fuels of dung, crop residues, wood and
charcoal.
--Daniel Kammen, "Cookstoves for the Developing World," Scientific American
In rural areas of many developing countries, women and
children may spend several hours a day collecting wood for cooking
or making charcoal, tasks that contribute to deforestation
and soil erosion.
--Daniel Kammen, "Cookstoves for the Developing World," Scientific American
If you use a coordinating conjunction to join two independent clauses, precede the coordinating conjunction with a comma. A comma is usually used before the coordinating conjunction that precedes the last item in a series of three or more items. For uses of the comma with coordinating conjunctions, see Coordinating Conjunctions Joining Independent Clauses and Elements in a Series.
In the past, many writers and readers considered that starting a sentence with a coordinating conjunction was poor style; however, this structure is now widely accepted.
Organic chemists have gained substantial command over the synthesis of
small complex molecules. But the goal of constructing large
well-defined molecules has been more elusive.
--Donald A. Tomalia, "Dendrimer Molecules," Scientific American
