In most compounds, the first part is logically an attribute of the second part, restricting its meaning. In some types of compounds, the parts stand on an equal basis; such compounds can be called copulative. Neither of the parts is an attribute of the other; rather, they are used together. For example, suomalais-amerikkalainen (Finnish-American) is something that is both Finnish and American, like a film produced in cooperation. If the first part has a compositive form, as discussed in the preceding section, that form is used, as in the example, instead of the basic form suomalainen.
Sometimes a compound has more than two coordinated parts, e.g. suomalais-amerikkalais-saksalainen (Finnish-American-German).
Copulative compounds are typically adjectives. Sometimes nouns are combined e.g. to indicate a combined profession or role, as in parturi-kampaaja (barber-hairdresser). Some names are copulative compounds, e.g. Itävalta-Unkari (Austria-Hungary), but e.g. modern company names that reflect fusions typically have special written form, e.g. TeliaSonera instead of the more logical Telia-Sonera. Combinations of surnames are conventionally written as copulative compounds, e.g. Virtanen-Lahtinen.
The parts of a copulative compound are normally separated by a hyphen (not an en dash “–”), and both parts have main stress on its first syllable, e.g. súomalais-ámerìkkalàinen. Thus, the construct acts phonetically as two words, but it is written as one word.
However, such a compound is written with a hyphen only if the parts are also similar in shape, not just parallel in meaning. Even though a word like sosioekonominen (socio-economic) is logically copulative, it is written without a hyphen. Pronunciation tends to follow the pattern of normal compounds, i.e. the second part has only secondary stress.
Similarly, we write afroaasialainen, but the alternative word afrikkalais-aasialainen (African-Aasian) is written with a hyphen and has primary stress on both parts.
There are old compounds that are logically copulative but written and pronounced as normal compounds, e.g. voileipä (sandwich, literally “butter-bread”) and mustavalkea (black and white), ylösalas (up and down), sinivalkoinen (blue and white), and similar color names.
Expressions like “quality-price ratio” logically have a copulative compound as their first part. In Finnish, such an expression as a whole is treated as a compound, but the written form varies a lot. The official rules allow two different styles, hinta-laatusuhde, with a single hyphen, and hinta–laatu-suhde, with an en dash and a hyphen. The latter is easier to understand and corresponds better to the structure of the word. Words of this type are typically pronounced with main stress with each of the primary constituents, i.e. as if they were three words: hínta láatu súhde. It is possible to use genitive attributes to avoid compounds of this type, e.g. hinnan ja laadun suhde, but this is not common.
The spelling alternative with an en dash can be used when the dash connects words that express participants in some sense. In words where the first part is a copulative compound expressing just e.g. ingredients, this is not possible, and the only accepted spelling is as in liha-makaronilaatikko (meat and macaroni casserole). When such words become common, they are often pronounced as normal compounds, e.g. líhamàkarònilàatikko, and often written without a hyphen.