A statement of what a learner is expected to have achieved or learned by the end of a lesson or programme of study, expressed in terms of observable behaviour. The objective will usually be prefixed, therefore, by a phrase such as ‘By the end of the lesson the learner will be able to …’. There should then follow a description of what is expected, including the standard to which it must be achieved. Thus, the sentence ‘By the end of the lesson the learner will be able to use the apostrophe correctly and appropriately indicate (a) possession and (b) abbreviation, and will be able to explain correctly the rules governing apostrophe use’ indicates exactly what is to be learned and what behaviours the learner must be required to demonstrate in order that valid assessment of their learning can take place. Such observable objectives can be helpful to the teacher in structuring the lesson, since they indicate not only what is to be learned, but also what learner activities are essential, and how the learning is to be assessed. For this reason, they are often used as a basis on which to construct a lesson plan, and appear within the lesson plan itself as pre‐specified learning outcomes. With the growth of competence‐based education and training in the last quarter of the 20th century, behavioural objectives flourished in the guise of competences in National Vocational Qualifications. However, useful as they may be in subjects where learning takes the form of observable behaviours, behavioural objectives may be irrelevant or inappropriate in other subject areas, particularly those involving higher‐order cognitive skills, or where learning takes place in the affective domain. Expressing an understanding of particle physics or an appreciation of Yeats's poetry, for example, in terms of observable behaviours to be assessed would almost certainly prove extremely difficult to do. Moreover, useful as pre‐specified outcomes may be in many learning situations, it can be argued that the setting of very precise behavioural objectives inevitably imposes constraints on the teacher and learner alike, and could act as an obstacle to inspiration on both sides. See also Bloom's Taxonomy.