This paper examines the incidence of verbal concord rule violation in educated Nigeria ESL against the conceptual framework of interference and "intraference". Intraference is a coinage for the "overgeneralization of linguistic material and semantic features" or "intralingual interference". The paper is basically intuitively theoretical and descriptive. Library research, the Internet, observation and recording of some linguistic events by educated Nigerians were used as sources of data collection. To achieve the effective teaching, learning, and use of verbal concord in ESL and EFL, formula N+s/S+s = V-s or N-s/S-s = V+s is proposed and illustrated with graded steps. The three major steps of the formula are (i) the explanation and application of the formula symbols, (ii) categorized teaching and learning of English plurality and (iii) explanation with illustration of the structural dynamics of English that constrain non-native users to produce verbal concord errors. This formula may be used to correct concord errors and enhance concord teaching and learning.