get term id by post id

1<?php $term_obj_list = get_the_terms( $post->ID, 'taxonomy_name' ); ?>

1// RETRIVE TERM SLUG ( for single.php or template-part )
2
3$terms = get_the_terms( $post->ID, 'your-taxonomy' );
4if ( !empty( $terms ) ){
5    // get the first term
6    $term = array_shift( $terms );
7    echo $term->slug;
8}

1INSIDE TAXONOMY PAGES
2$term      = get_queried_object();
3$term_id   = $term->term_id;