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tanru are Lojban metaphors. They are made up of gismu representing concepts that are related to the concept being communicated. The relationship isn't necessarily unambiguous in meaning, although the grammatical relationship between the words is unambiguous. A blue-nest in some way nests someone or something. It could be a nest for blue eggs, or blue people, or it could be a house painted blue either partially or completely. It takes a more elaborate tanru to distinguish these less ambiguously (if such is important), or non-tanru methods can be used to expand communication unambiguously. Most often, tanru will be appropriate. tanru are something like English adjective-noun and adverb-verb combinations. They go beyond these concepts by combining and expanding upon them. In this, they are similar to Chinese metaphor more than to English. In general, the gismu on the left modify those on the right, and all groupings are in pairs from the left. Thus

broda brode brodi brodo brodu

is a 5-part tanru. The meaning is interpreted by grouping gismu in pairs as:

(((broda brode) brodi) brodo) brodu

To change this unambiguous grouping, specific cmavo are used that allow unique expression of the possible groupings. The cmavo 'bo' causes two adjacent gismu to group together before any other groupings. Thus we get

((broda brode) (brodi bo brodo)) brodu

If there are two bo's in a tanru, the leftmost takes precedence, but this is unlikely to occur in normal usage. The cmavo 'ke' can be used to change the grouping. ke causes everything to the left of it to modify everything to theright; an example is:

broda ke (((brode brodi) brodo) brodu)

To terminate right-grouping before the end, close off with ke'e, the rightgrouping terminator cmavo:

(broda ke ((brode brodi) brodo) ke'e brodu)

The logical connectives and negation can be used to modify part or all of a tanru. The tanru logical connective cmavo are ja, je, jo, ju, and each of these can be negated using na (negates the term before the connective) and nai (negates the term after the connective). In addition, the mixed connectives of selma'o JOI and the abstraction cmavo of selma'o NU can modify the components of tanru, and numbers can be incorporated into tanru with the aid of selma'o MOI.

tanru-making is one of the most important skills in speaking Lojban, because tanru are the primary source of semantic ambiguity in the language. The essence of tanru interpretation depends on imaginatively thinking of possible meanings (using some simple conventions to limit the possibilities), and then determining why the speaker used this particular tanru as opposed to some other, thus weeding out the interpretations that are not intended by the speaker. To make a new tanru, the reverse process is used. Think of a few possibilities, then try to analyze how a listener might misinterpret each possibility. Thus, making tanru gets to the true essence of human communication: putting one's self in the mind of the other person, and figuring out what that mind is thinking. When thinking Lojbanically - seeing the world through tanru - one is to some extent practicing a form of mind-reading.

The following are two of the most basic of the tanru conventions:

Given a tanru which expresses an idea to be used frequently, it can be turned into a lujvo by following the lujvo-making algorithm. In building a lujvo, the first step is to replace each gismu with a rafsi that uniquely represents that gismu. (Some cmavo found in tanru are also assigned rafsi. If a cmavo embedded in a tanru does not have a rafsi, you may have to paraphrase the tanru in some way.) These rafsi are then attached together by fixed rules that allow the resulting compound to be recognized as a single word and to be broken down in only one way. Some conventions that have been adopted for this are listed at the end of this essay. There are four other complications: