倘 is a formal, literary conjunction meaning 'if' or 'supposing', used mainly in written Chinese. However, the pinyin provided here is cháng, which is unusual for this sense — the standard reading for the 'if' meaning is tǎng (as in 倘若). The reading cháng normally appears in the compound 倘佯 (to stroll). This row's data appears to have a pinyin mismatch; learners should be aware that the common pronunciation for the conjunction is tǎng.