A mathematical expression input electronic apparatus, comprising: mathematical expression display means for displaying a mathematical expression, said mathematical expression having been converted from a recognized voice; mathematical expression portion designation means for designating a mathematical expression portion displayed by the mathematical expression display means in accordance with user operation; conversion candidate data memory; and output means for determining a designation method for the mathematical expression portion designated by the mathematical expression designation means, modifying the mathematical expression in accordance with the designation method, and displaying the modified mathematical expression, wherein the output means comprises selection means for, when determining that the user designated an operator included in the mathematical expression as a designation method for the displayed mathematical expression portion, generating candidates for a mathematical expression with different mathematical expression portions to be incorporated by the designated operator, wherein the output means determines which of a forward portion and a backward portion of the mathematical expression the operator incorporates, searches for a delimiter in the determined forward and/or backward portion of the mathematical expression, if the delimiter found is determined not to be a head or an end of the mathematical expression, repeats the search for a delimiter for a further forward portion and/or backward portion of the mathematical expression, and stores a mathematical expression determined in association with a delimiter as a candidate in the conversion candidate data memory each time a new delimiter is found; and the selection means is configured to modify the mathematical expression based on a candidate selected by the user. mathematical expression display means for displaying a mathematical expression, said mathematical expression having been converted from a recognized voice; mathematical expression portion designation means for designating a mathematical expression portion displayed by the mathematical expression display means in accordance with user operation; conversion candidate data memory; and output means for determining a designation method for the mathematical expression portion designated by the mathematical expression designation means, modifying the mathematical expression in accordance with the designation method, and displaying the modified mathematical expression, wherein the output means comprises selection means for, when determining that the user designated an operator included in the mathematical expression as a designation method for the displayed mathematical expression portion, generating candidates for a mathematical expression with different mathematical expression portions to be incorporated by the designated operator, wherein the output means determines which of a forward portion and a backward portion of the mathematical expression the operator incorporates, searches for a delimiter in the determined forward and/or backward portion of the mathematical expression, if the delimiter found is determined not to be a head or an end of the mathematical expression, repeats the search for a delimiter for a further forward portion and/or backward portion of the mathematical expression, and stores a mathematical expression determined in association with a delimiter as a candidate in the conversion candidate data memory each time a new delimiter is found; and determines which of a forward portion and a backward portion of the mathematical expression the operator incorporates, searches for a delimiter in the determined forward and/or backward portion of the mathematical expression, if the delimiter found is determined not to be a head or an end of the mathematical expression, repeats the search for a delimiter for a further forward portion and/or backward portion of the mathematical expression, and stores a mathematical expression determined in association with a delimiter as a candidate in the conversion candidate data memory each time a new delimiter is found; and the selection means is configured to modify the mathematical expression based on a candidate selected by the user.