Disclosed is a segmental earth retaining wall block (1) having a front side (3), a top side (5) with a transversal tongue (7) of a given width projecting from it, the tongue (7) extending at a first distance (D1) from the front side (3), and a bottom side (9) with a transversal groove (11) made in it, the groove (11) being sized to receive the tongue (7) of another similar block (1) positioned below and thus to allow stacking of the blocks (1). The groove (11) extends at a second distance (D2) from the front side (3) that is smaller than the first distance (D1), and the first and second distances (D1,D2) are selected so that the tongue (7) and the groove (11) are offset with respect to each other over a distance that is smaller than the width of the tongue (7). Advantageously, the tongue (7) is provided with a splitting groove (13) sized and positioned to allow splitting of the tongue (7) with a splitting tool along a transversal line that is positioned to permit the remaining portion of this tongue to fit into the groove (11) of a further similar block (1) stacked on top of the present block with the front side (3) of this further similar block (1) extending in a same vertical plane as the first side of the present block (1). As a result, one may stack the above mentioned blocks (1) as such, the resulting wall being then battered, or one may stack the above mentioned blocks after having splitted their tongues, the resulting wall being then vertical.