span.trainingWord {
    display: inline-block;
    margin: 0 5px;
    color: gray;
    font-size: small;
    cursor: pointer;
    position: relative;
}

span.trainingWord:hover:after {
    position: absolute;
    top: 20px;
    left: 0;
    width: 200px;
    border: 1px solid gray;
    border-radius: 5px;
    background-color: #e2f7e0;
    font-size: small;
    padding: 5px;
    z-index: 10;

    content: attr(data-context);
}