ALTHOUGH (vaikka; siitä huolimatta että)
When used at the beginning of the sentence, "although" is equivalent in meaning to the other subordinators "though" and "even though". However, "although" is the most formal of these three, with "even though" and "though" being more commonly found in the less formal writing of magazines and newspapers. The subordinator "although" has two main uses:

Use "although" to introduce a complete clause (subject + verb) that both contrasts with a statement made in the main clause, as well as makes the following statement in the main clause seem surprising or unexpected. We call this the concessive use of "although".

Use "although" to admit a fact that should be considered less important than that stated in the main clause. We call this the adversative use of "although".

Use "although" to express surprise (concessive meaning)
Similar to "nevertheless", "despite" and "in spite of", "although", though and even though are
concessive connectors and can therefore be used to substitute for each other in the same types of sentences.

Subordinator + [subject + verb], [subject + verb]:

Although Swedish is one of Finland's two national languages, few Finns can actually speak it well enough to carry out an intelligible conversion.

[subject + verb] + Sentence connector + [subject + verb]:

Few Finns can actually speak Swedish well enough to carry out an intelligible conversion. Nevertheless, it is one of Finland's two national languages.

Preposition + [Noun / -ing form], [subject + verb]:

Despite its official status as one of Finland's two national languages, Swedish is spoken by very few Finns.

Use "although" to admit that a fact is less important
Often two clauses joined by the co-ordinate conjunction "but" in Finnish can be better expressed in
English with "although". Notice how both clauses are given equal stress by using "but", whereas
"although" allows the writer to clearly signal which information is more important.

Without focus:

There is no universal agreement within the scientific community on the impacts of increasing concentrations of greenhouse gases, but it has been theorized that they may lead to an increase in the average temperature of the Earth's surface.

Notice how moving the position of the subordinator in the two sentences below affects the emphasis and focus of the message (shown in bold).

Second (main) clause is more important:

Although there is no universal agreement within the scientific community on the impacts of increasing concentrations of greenhouse gases, it has been theorized that they may lead to an increase in the average temperature of the Earth's surface.

First (main) clause is more important:

There is no universal agreement among scientists and climatologists on the potential impacts of an increase in the average temperature of the Earth, although it has been hypothesized that it could lead to a variety of changes in the global climate, sea level, agricultural patterns, and ecosystems.

(EVEN) THOUGH (huolimatta siitä että, vaikkakin)

The subordinator "though" has the same meaning as "although" but sounds more informal. Use "though" to signal that the statement in the main clause is unexpected or surprising, or to admit a fact that should be considered less important than that stated in the main clause.

At the beginning of the sentence before the main clause, (even) though has the same function as although in introducing facts that either slightly contradict claims made in the main clause or make these claims seem unexpected or surprising.

When placed after the main clause, (even) though limits or reduces the strength of claims stated in the main clause.

Second (main) clause is more important:

(Even) though climate change cannot be predicted for a specific region, experience with natural climatic variability leads many scientists to believe that even relatively small changes to climate may be socially and economically significant.

First (main) clause is more important:

Climate change cannot be predicted for a specific region, (even) though experience with natural climatic variability leads many scientists to believe that even relatively small changes to climate may be socially and economically significant.

In informal spoken English, the subordinator "though" is often used incorrectly as a sentence connector with the meaning of "however", "nevertheless", or "nonetheless".

"Spoken" form:
Methane is released during coal-mining activities, oil exploration and when vegetation is burnt during land clearance. The main source of methane , though is agricultural activity.

"Written" form:
Methane is released during coal-mining activities, oil exploration and when vegetation is burnt during land clearance. The main source of methane, however, is agricultural activity.

WHILE / WHILST (kun taas)

The subordinator "while", and the slightly more emphatic "whereas", can be used to introduce information that contrasts with that stated in the main clause, or to signal that the information introduced by "while" is true, but that it does not affect the truth of the statement given in the main clause. In British English, "while" is often written as "whilst", a form unfamiliar to most North Americans.

Although "while" can appear both before and after the main clause, it tends to come at the beginning of the sentence, before the main clause. Conversely, "whereas" more frequently appears after the main clause.

Before main clause:

While land temperatures are measured by the temperature of air about a metre above the earth’s surface, ocean temperatures are measured by the temperature of water. (more common)

After main clause:

Land temperatures are measured by the temperature of air about a metre above the earth’s surface, while ocean temperatures are measured by the temperature of water. (less common)

Many novice writers tend to overestimate their readers' ability to interpret listings of facts and figures. A good example of this is the overuse of "and", when a contrastive connector would give more appropriate emphasis and focus to the sentence.

Unclear relationship:

Estimates for the year 2025 range from five to fifteen inches above current sea level, and estimates of the rise by 2100 range from two to four feet.

Emphasis on second clause:

While estimates for the year 2025 range from five to fifteen inches above current sea level, estimates of the rise by 2100 range from two to four feet.

"WHILE": adversative connectors

Similar to "on the other hand" and "in contrast", "while" ( UK "whilst") and whereas are adversative connectors and can therefore be used to substitute for each other in the same types of sentences.

Subordinate + [subject + verb], [subject + verb]:

While Japanese politicians and corporations are enthusiastic about nuclear power, the Japanese people are very allergic to anything nuclear, particularly after they experienced several very dangerous nuclear accidents in the last several years in their own nuclear facilities.

[subject + verb] + Sentence connector + [subject + verb]:

Japanese politicians and corporations are enthusiastic about nuclear power. In contrast, the Japanese people are very allergic to anything nuclear, particularly after they experienced several very dangerous nuclear accidents in the last several years in their own nuclear facilities.

Preposition + [Noun / -ing form]:

Unlike Japanese politicians and corporations, who are enthusiastic about nuclear power, the Japanese people are very allergic to anything nuclear, particularly after they experienced several very dangerous nuclear accidents in the last several years in their own nuclear facilities.

WHEREAS (kun sitä vastoin)

Although basically having the same meaning as "while", "whereas" is more emphatic, tends to come after the main clause, and tends to contrast opposite sides of a single quality in two similar things. Thus, "whereas" is used to contrast between extreme examples that represent almost polar opposites of each other. "While", on the other hand, only signals that two things differ, and not that they are opposites. This makes "While" ideal for comparing numbers and statistics, as is common in the results sections of research reports.

Difference between sets of data

While estimates for the year 2025 range from five to fifteen inches above current sea level, estimates of the rise by 2100 range from two to four feet.

Polar opposites

The Finns had difficulty supplying their troops with ammunition, whereas the Russians had an unlimited supply and a vastly superior system of communication.

"WHEREAS": adversative connectors

Similar to "on the other hand" and "in contrast", both "whereas" and "while" are adversative connectors and can therefore be used to substitute for each other in the same types of sentences.

[subject + verb], [subject + verb] + Subordinate:

Nuclear energy fuel uses only about 4 percent fissionable uranium, whereas a nuclear weapon uses 100 percent fissionable uranium. Because of this difference, nuclear power plants cannot explode.

[subject + verb] + Sentence connector + [subject + verb]:

Nuclear energy fuel uses only about 4 percent fissionable uranium. In contrast, a nuclear weapon uses 100 percent fissionable uranium. Because of this difference, nuclear power plants cannot explode.

Preposition + [Noun / -ing form]:

Unlike a nuclear weapon using 100 percent fissionable uranium, nuclear energy fuel uses only about 4 percent fissionable uranium.