Panel, especially floor panel, having - a core of wood-based material or a wood-based material/plastic mixture, - an upper side and an underside, wherein - the panel (1, 2) has at at least two mutually opposite lateral edges (I, II) a mutually corresponding profiling such that two identically formed panels (1, 2) can be connected and locked to one another in the horizontal direction and in the vertical direction by a substantially vertical joining movement, - the locking in the horizontal direction can be effected by a hook connection with an upper locking portion having a hook element and with a lower locking portion having a hook element, - the locking in the vertical direction can be effected by at least one tongue element which can be moved in the horizontal direction, - the at least one tongue element is provided on a lateral edge, - the at least one tongue element - is formed in one piece from the core, - is formed on the lower locking portion, - snaps in during the joining movement behind a locking edge extending substantially in the horizontal direction, characterized in that - the at least one tongue element is free with respect to the core in the direction of the opposite lateral edge by means of a substantially vertical slot and is connected at its two ends (6a, 6b) to the core in the longitudinal direction of the lateral edge, and in that - the substantially vertical slot has at its two ends (7a, 7b) transition regions at which the substantially vertical slot is formed not through the lower locking portion but as a gap with a substantially uniformly decreasing depth. - a core of wood-based material or a wood-based material/plastic mixture, - an upper side and an underside, wherein - the panel (1, 2) has at at least two mutually opposite lateral edges (I, II) a mutually corresponding profiling such that two identically formed panels (1, 2) can be connected and locked to one another in the horizontal direction and in the vertical direction by a substantially vertical joining movement, - the locking in the horizontal direction can be effected by a hook connection with an upper locking portion having a hook element and with a lower locking portion having a hook element, - the locking in the vertical direction can be effected by at least one tongue element which can be moved in the horizontal direction, - the at least one tongue element is provided on a lateral edge, - the at least one tongue element - is formed in one piece from the core, - is formed on the lower locking portion, - snaps in during the joining movement behind a locking edge extending substantially in the horizontal direction, - is formed in one piece from the core, - is formed on the lower locking portion, - snaps in during the joining movement behind a locking edge extending substantially in the horizontal direction, - the at least one tongue element is free with respect to the core in the direction of the opposite lateral edge by means of a substantially vertical slot and is connected at its two ends (6a, 6b) to the core in the longitudinal direction of the lateral edge, and in that - the substantially vertical slot has at its two ends (7a, 7b) transition regions at which the substantially vertical slot is formed not through the lower locking portion but as a gap with a substantially uniformly decreasing depth.