The phrase 'study at pay' refers to the idea of pursuing higher education while paying for it. There are various synonyms you could use instead of this phrase, depending on the context and the level of education. Some of these include 'paying tuition fees', 'enrolling for classes on a fee basis', 'enrolling in a degree program with tuition', or simply 'enrolling in a paid course'. The idea of studying at pay is not a new one, and many students opt for this approach due to its flexibility and convenience. So whether you choose to study at pay or enroll in a paid course, the key is to keep learning and growing.