In most cases, an assistant lecturer is a young professor at a British or Irish university. The promotion track in English academia begins with the appointment of assistants, who can be promoted to senior lecturers, professors, and finally readers. Lecturers are the U.S.-equivalent of junior professors. In the United States, the term “assistant lecturer” is also used, but refers to a whole other class of university jobs. A person who is an assistant lecturer in an American university is non-permanent and is usually hired only to deliver lectures in a certain course or set of courses.
This lecturer is a permanent faculty member in a university following the English system. He or she is usually responsible for teaching all aspects of certain courses within his or her discipline. Lecturers prepare lessons and engage with students, but also participate in the wider university community. They often sit on academic panels, participate in university committees, and help shape the departments in which they work.
Assistant lecturers are career academics. They have devoted their lives to the pursuit of knowledge and the installation of that knowledge in younger generations. A typical assistant is a teacher devoted the education of the whole student. He or she also typically does considerable independent research, usually in hopes of publication.
The amount of time that a person must serve as an assistant lecturer before being promoted to senior lecturer depends on the university, but is usually a period of at least five years. Senior lecturers can be promoted to full professors or, in the oldest universities, readers. These lecturers are in many ways viewed as junior professors who can be promoted with time and on a showing of good works. Academics who hold the "professor" title are more senior, exercise greater control over course selection, and often command a higher pay. Promotion to reader status is usually reserved for professors emeritus or those senior-most scholars nearing retirement.
In many ways, the British position mirrors the U.S. assistant professor position. Assistant professors have largely the same junior status and are usually also awaiting promotion to rise through the ranks of an academic department. Some U.S. universities advertise assistant lecturerships, but these positions are very different from assistant professors.
An assistant lecturer in the U.S. system is usually a temporary faculty member, often hired on a course-by-course basis. He or she will come to campus to teach a single course but does not often maintain an office and certainly does not participate in the university community the way a permanent faculty member would. Lecturers in this context are often subject matter experts or tenured professors at nearby colleges. It is hard to become an assistant lecturer in the U.S. without a certain degree of expertise.
Someone who is a successful businessman might accept a lecturer position at a university to teach a single course on business management, for instance. Similarly, a well-respected scholar at one university might be hired by another school on a contract basis to teach one or two classes. The assistant lecturer position in the U.S. is not designed to ripen into a full academic professorship and neither is it meant to be permanent.